ast@cs.vu.nl (Andy Tanenbaum) (12/18/89)
#master
Command: master - control the creation of shervers
Syntax: master count uid gid command
Flags: (none)
Example: master 2 1 1 /bin/sherver port# Start 2 shervers
If a machine is intended to be used as a server, its /etc/rc file should
have a command similar to the example above. When the system is booted, master
runs and forks off the required number of shervers (shell servers), up to a
maximum of four. They run with the indicated uid and gid, and listen to the
indicated port. When an rsh is done on a client machine, the command is given
to one of the shervers for execution. When the sherver is done, it exits, mas-
ter, which is always running, sees this, and creates a new sherver. Thus master
is very similar to init, only it makes new shervers (usually) instead of new
login programs. Master must run as root to be able to do setuid and setgid.
#mined
Command: mined - MINIX editor
Syntax: mined [file]
Flags: (none)
Examples: mined /user/ast/book.3 # Edit an existing file
mined # Call editor to create a new file
ls -l | mined # Use mined as a pager to inspect listing
Mined (pronounced min-ed) is a simple full-screen editor. When editing a
file, it holds the file in memory, thus speeding up editing, but limiting the
editor to files of up to about 43K. Larger files must first be cut into pieces
by split. Lines may be arbitrarily long. Output from a command may be piped
into mined so it can be viewed without scrolling off the screen.
At any instant, a window of 24 lines is visible on the screen. The current
position in the file is shown by the cursor. Ordinary characters typed in are
inserted at the cursor. Control characters and keys on the numeric keypad (at
the right-hand side of the keyboard) are used to move the cursor and perform
other functions.
Commands exist to move forward and backward a word, and delete words. A
word in this context is a sequence of characters delimited on both ends by
white space (space, tab, line feed, start of file, or end of file). The com-
mands for deleting characters and words also work on line feeds, making it pos-
sible to join two consecutive lines by deleting the line feed between them.
The editor maintains one save buffer (not displayed). Commands are present
to move text from the file to the buffer, from the buffer to the file, and to
write the buffer onto a new file. If the edited text cannot be written out due
to a full disk, it may still be possible to copy the whole text to the save
buffer and then write it to a different file on a different disk with CTRL-Q.
It may also be possible to escape from the editor with CTRL-S and remove some
files.
Some of the commands prompt for arguments (file names, search patterns,
etc.). All commands that might result in loss of the file being edited prompt
to ask for confirmation.
A key (command or ordinary character) can be repeated n times by typing ESC
n key where ESC is the ``escape'' key.
Forward and backward searching requires a regular expression as the search
pattern. Regular expressions follow the same rules as in the UNIX editor, ed:
1. Any displayable character matches itself.
2. . (period) matches any character except line feed.
3. ^ (circumflex) matches the start of the line.
4. $ (dollar sign) matches the end of the line.
5. \c matches the character c (including period, circumflex, etc).
6. [string] matches any of the characters in the string.
7. [^string] matches any of the characters except those in the string.
8. [x-y] matches any characters between x and y (e.g., [a-z]).
9. Pattern* matches any number of occurrences of pattern.
Some examples of regular expressions are:
The boy matches the string ``The boy''
^$ matches any empty line.
^A.*\.$ matches any line starting with an A, ending with a period.
^[A-Z]*$matches any line containing only capital letters (or empty).
[A-Z0-9]matches any line containing either a capital letter or a digit.
Control characters cannot be entered into a file simply by typing them
because all of them are editor commands. To enter a control character, depress
the ALT key, and then while holding it down, hit the ESC key. Release both ALT
and ESC and type the control character. Control characters are displayed in
reverse video.
The mined commands are as follows.
CURSOR MOTION
arrows Move the cursor in the indicated direction
CTRL-A Move cursor to start of current line
CTRL-Z Move cursor to end of current line
CTRL-^ Move cursor to top of screen
CTRL-_ Move cursor to end of screen
CTRL-F Move cursor forward to start of next word
CTRL-B Move cursor backward to start of previous word
SCREEN MOTION
Home key Move to first character of the file
End key Move to last character of the file
PgUp key Scroll window up 23 lines (closer to start of the file)
PgDn key Scroll window down 23 lines (closer to end of the file)
CTRL-U Scroll window up 1 line
CTRL-D Scroll window down 1 line
MODIFYING TEXT
Del key Delete the character under the cursor
Backspace Delete the character to left of the cursor
CTRL-N Delete the next word
CTRL-P Delete the previous word
CTRL-T Delete tail of line (all characters from cursor to end of line)
CTRL-O Open up the line (insert line feed and back up)
CTRL-G Get and insert a file at the cursor position
BUFFER OPERATIONS
CTRL-@ Set mark at current position for use with CTRL-C and CTRL-K
CTRL-C Copy the text between the mark and the cursor into the buffer
CTRL-K Delete text between mark and cursor; also copy it to the buffer
CTRL-Y Yank contents of the buffer out and insert it at the cursor
CTRL-Q Write the contents of the buffer onto a file
MISCELLANEOUS
numeric + Search forward (prompts for regular expression)
numeric - Search backward (prompts for regular expression)
numeric 5 Display the file status
CTRL-] Go to specific line
CTRL-R Global replace pattern with string (from cursor to end)
CTRL-L Line replace pattern with string
CTRL-W Write the edited file back to the disk
CTRL-X Exit the editor
CTRL-S Fork off a shell (use CTRL-D to get back to the editor)
CTRL-\ Abort whatever the editor was doing and wait for command
CTRL-E Erase screen and redraw it
CTRL-V Visit (edit) a new file
#mkdir
Command: mkdir - make a directory
Syntax: mkdir directory ...
Flags: (none)
Examples: mkdir dir # Create dir in the current directory
mkdir /user/ast/dir # Create the specified directory
The specified directory or directories are created. The entries . and ..
are inserted into the new directory.
#mkfs
Command: mkfs - make a file system
Syntax: mkfs special prototype
Flags: -L Make a listing on standard output
Examples: mkfs /dev/fd1 proto # Make a file system on /dev/fd1
mkfs /dev/fd1 360 # Make empty 360 block file system
Mkfs builds a file system and copies specified files to it. The prototype
file tells which directories and files to copy to it. If the prototype file
cannot be opened, and its name is just a string of digits, an empty file system
will be made with the specified number of blocks. A sample prototype file fol-
lows. The text following the # sign is comment. In the real prototype file,
comments are not allowed.
boot # boot block file (ignored)
360 63 # blocks and i-nodes
d--755 1 1 # root directory
bin d--755 2 1 # bin dir: mode (755), uid (2), gid (1)
sh ---755 2 1 /user/ast/shell # shell has mode rwxr-xr-x
mv -u-755 2 1 /user/ast/mv # u = SETUID bit
login -ug755 2 1 /user/ast/login# SETUID and SETGID
$ # end of /bin
dev d--755 2 1 # special files: tty (char), fd0 (block)
tty c--777 2 1 4 0 # uid=2, gid=1, major=4, minor=0
fd0 b--644 2 1 2 0 360 # uid, gid, major, minor, blocks
$ # end of /dev
user d--755 12 1 # user dir: mode (755), uid (12), gid (1)
ast d--755 12 1 # /user/ast
$ # /user/ast is empty
$ # end of /user
$ # end of root directory
The first entry on each line (except the first 3 and the $ lines, which ter-
minate directories) is the name the file or directory will get on the new file
system. Next comes its mode, with the first character being -dbc for regular
files, directories, block special files and character special files, respec-
tively. The next two characters are used to specify the SETUID and SETGID
bits, as shown above. The last three characters of the mode are the rwx pro-
tection bits.
Following the mode are the uid and gid. For special files, the major and
minor devices are needed. The size in blocks must also be specified for block
special files (the MINIX block size is 1K; this can only be changed by changing
BLOCK_SIZE and then recompiling the operating system).
#mknod
Command: mknod - create a special file
Syntax: mknod file [b] [c] major minor
Flags: (none)
Example: mknod /dev/plotter c 7 0 # Create special file for a plotter
Mknod creates a special file named file, with the indicated major and minor
device numbers. The second argument specifies a block or character file.
#more
Command: more - pager
Syntax: more [-cdflpsu] [-n] [+n] [+/pattern] [file] ...
Flags: -d Display prompt message at each pause
-f Do not fold lines
-l Do not treat CTRL-L as form feed
-p Page mode. Do not scroll
-s Suppress multiple blank lines
-u Use escape sequences for underlining
Examples: more file # Display file on the screen
more -p file1 file2 # Display two files in page mode
more -10 file # Use a 10 line window
more +/begin file # Hunt for the string begin
More is a pager that allows one to examine files. This program is patterned
after one originally produced at the University of California, Berkeley. When
more starts up, it displays a screenful of information from the first file in
its list, and then pauses for one of the following commands. In this descrip-
tion, # represents an integer telling how many of something.
<space> - Display next page
<return> - Display next line
CTRL-B - Go backward half a screenful
CTRL-D - Go forward half a screenful
CTRL-L - Redisplay the screen
#<space> - Go forward # lines
= - Print current line number
. - Repeat previous command
' - (single quote) Go back to start of last search
! - Escape to a shell
#/<expr> - Go to #-th occurrence of <expr>
:f - Display current file name and line number
#:n - Skip forward # files
#:p - Skip backward # files
b - Go backward half a screenful
d - Go forward half a screenful
#f - Skip # screenfuls
h - Display /usr/lib/more.help
#n - Go to #-th occurence of last <expr>
q - Quit more
Q - Quit more
#s - Skip # lines
v - Try to execute /usr/bin/vi
#z - Go forward # lines and set screen size to #
For the benefit of users who always want to use certain flags when calling
more, the shell variable MORE can be set to the desired default flags, for
example, MORE="-p".
#mount
Command: mount - mount a file system
Syntax: /etc/mount special file [-r]
Flags: -r File system is mounted read-only
Example: /etc/mount /dev/fd1 /user # Mount floppy disk 1 on /user
The file system contained on the special file is mounted on file. In the
example above, the root directory of the file system in drive 1 can be accessed
as /user after the mount. When the file system is no longer needed, it must be
unmounted before being removed from the drive.
#mref
Command: mref - make listing and cross reference map of MINIX
Syntax: mref [-n] [-dlmtsx] [-p page] file ...
Flags: -n Number of lines to print per page, default = 50
-d Don't produce definition file (global symbol table)
-l Don't produce listing
-m Multiple reference on one line only are cited only once
-p n Set initial page number to n
-t Generate troff macro call before each page
-s Suppress line numbering between procedures
-x Don't produce the cross reference map
Examples: mref *.[hc] # List and cross reference files .h and .c
mref -60 -t *.c # Produce troff input at 60 lines/page
mref -dx -p 100 *.c # Listing only, first page is numbered 100
In default mode, mref produces three output files: a numbered listing of the
input files (on standard output), a global symbol table (on symbol.out), and a
cross reference map to the global symbols (on xref.out). A global symbol in
this context is one present in a #define, PUBLIC, PRIVATE, or SYMBOL statement
(the latter being introduced to allow users to explicitly declare certain sym-
bols as global). Any of the three outputs can be suppressed, or alternatively,
be made suitable for input to troff for typesetting.
#mv
Command: mv - move or rename a file
Syntax: mv file1 file2
mv file ... directory
Flags: (none)
Examples: mv oldname newname # Move oldname to newname
mv file1 file2 /user/ast # Move two files to /user/ast
Mv moves one or more files from one place in the file system to another. If
the old path and new path are on the same device, it is done by linking and
unlinking, otherwise by copying.
#nm
Command: nm - print name list
Syntax: nm [-gnopru] [file] ...
Flags: -g Print only external symbols
-n Sort numerically rather than alphabetically
-o Prepend file name to each line rather than only once
-p Don't sort, print in symbol-table order
-r Sort in reverse order
-u Print only undefined symbols
Examples: -nm -n a.out # Print all symbols in numerical order
-nm -g a.out # Print global symbols alphabetically
Nm prints the symbol table of executable files when it is available. If no
file is given, the symbols in a.out are used. The format of the table is some-
what compatible with the one produced by asld when used with the -s option.
The symbol table can be added with ast. Archives are not supported. Note that
assembly language files don't have symbol tables.
#nro
Command: nro - text formatter
Syntax: nro [-bv] [+n] [-n] [-mmacros] [-pn] [file] ...
Flags: +n First page to print
-n Last page to print
-b Output device can backspace
-m Use /usr/lib/tmac/tmac.macros
-p Shift each line n spaces right
-v Print nro version number
Examples: nro infile >outfile # Format infile
nro +3 -5 infile >outfile # Only output pages 3-5
Nro is a text formatter patterned loosely on nroff, but much simpler.
Unlike roff, it accepts parametrized macros. The commands are given in the
file /usr/doc/nro.doc.
#od
Command: od - octal dump
Syntax: od [-bcdhox] [file] [ [+] offset [.][b] ]
Flags: -b Dump bytes in octal
-c Dump bytes as ASCII characters
-d Dump words in decimal
-h Print addresses in hex (default is octal)
-o Dump words in octal (default)
-x Dump words in hex
Examples: od -ox file # Dump file in octal and hex
od -d file +1000 # Dump file starting at byte 01000
od -c file +10.b # Dump file starting at block 10
Od dumps a file in one or more formats. If file is missing, stdin is
dumped. The offset argument tells od to skip a certain number of bytes or
blocks before starting. The offset is in octal bytes, unless it is followed by
a ``.'' for decimal or b for blocks or both.
#passwd
Command: passwd - change a login password
Syntax: passwd [name]
Flags: (none)
Examples: passwd # Change current user's password
passwd ast # Change ast's password (super-user only)
Passwd is used to change your password. It prompts for the old and new
passwords. It asks for the new password twice, to reduce the effect of a typ-
ing error. Do not forget to copy the modified password file back to the root
file system diskette, or the changes will be lost when the system is rebooted.
#paste
Command: paste - paste multiple files together
Syntax: paste [-s] [-dc] file...
Flags: -s Print files sequentially, file k on line k
-dc Set delimiter used to separate columns
Examples: paste file1 file2 # Print file1 in col 1, file2 in col 2
paste -s f1 f2 f3 f4 # Print f1 on line 1, f2 on line 2, etc
Paste displays multiple files in parallel. Suppose a set of k files each
have one word per line. Then the paste output will have k columns, with the
contents of file j in column j. The columns are separate by tabs unless the
separator is changed with the -d flag. If the -s flag is given, then the first
file is on line 1, the second file on line 2, etc. In effect, -s turns the out-
put sideways.
#patch
Command: patch - patches up a file from the original and a diff
Syntax: patch [-DFNbcdeflnop]
Flags: -D Mark changes with #ifdef...#endif next arg gives label
-F Sets the maximum fuzz factor
-N Ignore patches that are reversed or already applied
-b Next argument is backup extension, instead of .orig
-c Interpret the patch file as a context diff
-d Cd to the next arg (assumed a dir) before doing anything
-e Interpret the patch file as an ed script
-f Forces patch to do its work without asking any questions
-l Do matching loosely (e.g., all white space is equivalent)
-n Interpret the patch file as a normal diff
-o Next argument is the output file name
-p Sets the pathname strip count
Examples: patch file difflist # Fix up file
patch <difflist # Patch multiple files
Patch takes an original file and a diff listing and recreates the new file.
It is functionally similar to fix, but much more powerful. Not only can it
handle normal diffs, but also context diffs produced by cdiff. In addition, it
works even when the file being patched has other changes to it. It deduces the
type of difflist itself (unless given -c, -e, or -n). The normal usage is
given in the example above. In this case patch will modify 'file' to incor-
porate all the patches. The original file will be saved to a file ending in a
tilde.
If no input file is given, patch reads stdin which may contain the
concatenation of multiple diff listings. In this way, all the files in a
directory may be updated at once.
#pr
Command: pr - print a file
Syntax: pr [[option] ... [-columns] [+page] [file] ...
Flags: -h Take next argument as page header
-l Sets page length in lines
-n Number the output lines
-t Do not print page header or trailer
-w Sets line length in characters
Examples: pr -w72 -l60 file # Use 72 character line, 60 line page
pr -3 file # List file three columns to a page
pr +4 file # Start printing with page 4
Pr formats one or more files for printing. If no files are specified, stdin
is printed. Options are provided for setting the width and height of the page,
the number of columns to use (default 1), and the page to start with, among
others.
#pretty
Command: pretty - MINIX pretty printer
Syntax: pretty file ...
Flags: (none)
Example: pretty file1 file2 # Convert two files to MINIX layout
Pretty converts one or more C source files to MINIX format by changing their
layout. Running this program does not affect the resulting binary programs.
Actually, pretty is a postprocessor for indent, which must be installed in /bin
or /usr/bin. Although the output is not bad, it is not entirely consistent
with the book or even with itself.
#prep
Command: prep - prepare a text file for statistical analysis
Syntax: prep [file]
Flags: (none)
Example: prep infile >outfile # Prepare infile
Prep strips off most of the troff commands from a text file and then outputs
all the words, one word per line, in the order they occur in the file. This
file can then be sorted and compared to a dictionary (as a spelling checker),
or used for statistical analyses.
#printenv
Command: printenv - print out the current environment
printenv
Flags: (none)
Example: printenv # Print the environment
Printenv prints out the current environment strings, one per line.
#printroot
Command: printroot - print the name of the root device on standard output
Syntax: printroot
Flags: (none)
Example: printroot # Print the name of the root device
Printroot is useful for initializing the /etc/mtab entry when the system is
booted. It figures out what the root device is by searching /dev until it
finds a block special file with the right major/minor device numbers.
#pwd
Command: pwd - print working directory
Syntax: pwd
Flags: (none)
Example: pwd # Print the name of the working directory
The full path name of the current working directory is printed.
#rcp
Command: rcp - remote copy
Syntax: rcp [mach1]!file1 [mach2]!file2
Flags: (none)
Examples: rcp file mach1!/usr/ast/x # Local file to remote machine
rcp mach2!/usr/ast/x file # Fetch remote file x
Rcp is not a program. It is a shell script that does remote copying. It
makes use of the programs to and from.
#readall
Command: readall - read a device quickly to check for bad blocks
Syntax: readall file
Flags: (none)
Example: readall /dev/hd0 # Read all of /dev/hd0
Readall reads all of the named device in large chunks. It reports about
blocks that it cannot read. Unlike diskcheck, it does not attempt to write on
the disk, making it safer to use when one is worried about a sick system.
#readclock
Command: readclock - read the AT's real time clock
Syntax: readclock
Flags: (none)
Example: date `/usr/bin/readclock` </dev/tty# Useful in /etc/rc
Readclock reads the AT's real time clock and prints the result in a form
useful to date, namely, MMDDYYhhmmss. If the clock does not exist (e.g., on a
PC), it outputs "-q" to query the user for the time. The example given above
can be put in /etc/rc to load the real time when the system is booted.
#readfs
Command: readfs - read a MINIX file system
Syntax: readfs [-il] block_special [dir]
Flags: -i Give information about the file, but do not extract files
-l List the files extracted on standard output
Example: readfs -l /dev/fd0 # List contents of floppy disk
Readfs reads a floppy disk containing a MINIX file system. It can extract
all the files from it, give a listing of them, or both. The files extracted
can be put in a user-specified directory (default: current directory). If sub-
directories are needed, they will be created automatically.
#recover
Command: recover - recover files that have been removed.
Syntax: recover file ...
Flags: (none)
Examples: rm x; recover x # Unremove x
recover a b c # Recover three files
MINIX allows files that have been deleted (e.g., with rm) to be restored (in
/tmp). The trick is that when a file is unlinked, its i-node number is kept in
the directory entry. As long as the directory entry and disk blocks are not
reused, the file can be recovered. This program is actually just a little
front end for de, which must be installed and executable.
#rev
Command: rev - reverse the characters on each line of a file
Syntax: rev [file] ...
Flags: (none)
Example: rev file # Reverse each line
Each file is copied to standard output with all the characters of each line
reversed, last one first and first one last.
#rm
Command: rm - remove a file
Syntax: rm [-fir] name ...
Flags: -f Forced remove: no questions asked
-i Interactive remove: ask before removing
-r Remove directories too
Examples: rm file # Remove file
rm -i *.c # Remove .c files, asking about each
Rm removes one or more files. If a file has no write permission, rm asks
for permission (type ``y'' or ``n'') unless -f is specified. If the file is a
directory, it will be recursively descended and removed if and only if the -r
flag is present.
#rmdir
Command: rmdir - remove a directory
Syntax: rmdir directory ...
Flags: (none)
Examples: rmdir /user/ast/foobar # Remove directory foobar
rmdir /user/ast/f* # Remove 0 or more directories
The specified directories are removed. Ordinary files are not removed.
#roff
Command: roff - text formatter
Syntax: roff [-hs] [+n] [-n] file ...
Flags: -h Expand tabs to spaces in output
-s Stop before each page; continue on DEL
+n Start printing with page n
n Stop after page n
Examples: roff file # Run off file
roff +5 file # Run off file starting at page 5
Roff is a text formatter. Its input consists of the text to be output,
intermixed with formatting commands. A formatting command is a line containing
the control character followed by a two character command name, and possibly
one or more arguments. The control character is initially ``.'' (dot). The
formatted output is produced on standard output.
The formatting commands are listed below, with n being a number, c being a
character, and t being a title. A + before n means it may be signed, indicat-
ing a positive or negative change from the current value. Initial values for
n, where relevant, are given in parentheses.
.ad Adjust right margin.
.ar Arabic page numbers.
.br Line break. Subsequent text will begin on a new line.
.bl n Insert n blank lines.
.bp +n Begin new page and number it n. No n means +1.
.cc c Control character is set to c.
.ce n Center the next n input lines.
.de zz Define a macro called zz. A line with ``..'' ends definition.
.ds Double space the output. Same as .ls 2.
.ef t Even page footer title is set to t.
.eh t Even page header title is set to t.
.fi Begin filling output lines as full as possible.
.fo t Footer titles (even and odd) are set to t.
.hc c The character c (e.g., %) tells roff where hyphens are permitted.
.he t Header titles (even and odd) are set to t.
.hx Header titles are suppressed.
.hy n Hyphenation is done if n is 1, suppressed if it is 0. Default is 1.
.ig Ignore input lines until a line beginning with ``..'' is found.
.in n Indent n spaces from the left margin; force line break.
.ix n Same as .in but continue filling output on current line.
.li n Literal text on next n lines. Copy to output unmodified.
.ll +n Line length (including indent) is set to n (65).
.ls +n Line spacing: n (1) is 1 for single spacing, 2 for double, etc.
.m1 n Insert n (2) blank lines between top of page and header.
.m2 n Insert n (2) blank lines between header and start of text.
.m3 n Insert n (1) blank lines between end of text and footer.
.m4 n Insert n (3) blank lines between footer and end of page.
.na No adjustment of the right margin.
.ne n Need n lines. If fewer are left, go to next page.
.nn +n The next n output lines are not numbered.
.n1 Number output lines in left margin starting at 1.
.n2 n Number output lines starting at n. If 0, stop numbering.
.ni +n Indent line numbers by n (0) spaces.
.nf No more filling of lines.
.nx f Switch input to file f.
.of t Odd page footer title is set to t.
.oh t Odd page header title is set to t.
.pa +n Page adjust by n (1). Same as .bp
.pl +n Paper length is n (66) lines.
.po +n Page offset. Each line is started with n (0) spaces.
.ro Page numbers are printed in Roman numerals.
.sk n Skip n pages (i.e., make them blank), starting with next one.
.sp n Insert n blank lines, except at top of page.
.ss Single spacing. Equivalent to .ls 1.
.ta Set tab stops, e.g., .ta 9 17 25 33 41 49 57 65 73 (default).
.tc c Tabs are expanded into c. Default is space.
.ti n Indent next line n spaces; then go back to previous indent.
.tr ab Translate a into b on output.
.ul n Underline the letters and numbers in the next n lines.
#rsh
Command: rsh - remote shell for networking
rsh port [-beil]
Flags: -b Start the rsh in the background
-e Keep stderr separate from stdout
-i Take input from the local process
Examples: rsh machine5 # ls
rsh abc cat /usr/doc/f >f # Fetch remote file
rsh foobar # Log onto remote machine
The remote shell command is the way to have a distant server carry out a
command over the Ethernet. The port given as the first argument can be any
string of up to 6 characters, but it must match the port used by some sherver.
The command will be executed and the results returned on stdout. Unless the -e
flag is given, the remote stderr and stdout are merged onto the local stdout.
Giving rsh with just a port and no argument is the standard way to log onto a
remote machine.
#rz
Command: rz - receive a file using the zmodem protocol
Syntax: rz [-abepquvy] [-t timeout]
Flags: -a CP/M to UNIX conventions
-b Binary file
-e Escape for all control characters
-p Protect file if it already exists
-q Quiet; opposite of verbose
-t Set timeout in tenths of a second
-v Verbose; opposite of quiet
-y Yes, clobber existing files
Examples: rz </dev/tty1 >/dev/tty1 # Receive a file
Rz is a program that accepts a file sent from another computer using the
zmodem protocol. It is a highly complex program. See the /usr/doc/rz.doc and
/usr/doc/sz.doc files for more information.
#sed
Command: sed - stream editor
Syntax: sed [-f script_file] [edit_script] [file]
Flags: -f The following argument contains the edit script
Examples: sed -f script <file # Run a sed script on file
sed '/pig/s//hog/g' <file # Replace pig by hog in the file
Sed is a stream editor. It takes an edit script either from its argument or
a file, and performs an edit session on a named file or stdin, producing output
on stdout.
#sh
Command: sh - shell
sh [file]
Flags: (none)
Example: sh < script # Run a shell script
Sh is the shell. It permits redirection of input and output, pipes, magic
characters, background processes, shell scripts and most of the other features
of the V7 (Bourne) shell. A few of the more common commands are listed below:
date # Regular command
sort <file # Redirect input
sort <file1 >file2 # Redirect input and output
cc file.c 2>error # Redirect standard error
a.out >f 2>&1 # Combine standard output and standard error
sort <file1 >>file2 # Append output to file2
sort <file1 >file2 & # Background job
(ls -l; a.out) & # Run two background commands sequentially
sort <file | wc # Two-process pipeline
sort <f | uniq | wc # Three-process pipeline
ls -l *.c # List all files ending in .c
ls -l [a-c]* # List all files beginning with a, b, or c
ls -l ? # List all one-character file names
ls \? # List the file whose name is question mark
ls '???' # List the file whose name is three question marks
v=/usr/ast # Set shell variable v
ls -l $v # Use shell variable v
PS1='Hi! ' # Change the primary prompt to Hi!
PS2='More: ' # Change the secondary prompt to More:
ls -l $HOME # List the home directory
echo $PATH # Echo the search path
if ... then ... else ... fi # If statement
for ... do ... done # Iterate over argument list
while ... do ... done # Repeat while condition holds
case ... esac # Select clause based on condition
echo $? # Echo exit status of previous command
echo $$ # Echo shell's pid
echo $# # Echo number of parameters (shell script)
echo $2 # Echo second parameter (shell script)
echo $* # Echo all parameters (shell script)
#shar
Command: shar - shell archiver
Syntax: shar file ...
Flags: (none)
Examples: shar *.c >s # Collect C programs in shell archive
sh <s # Extract files from a shell archive
The named files are collected together into a shell archive written onto
standard output. The individual files can be extracted by redirecting the
shell archive into the shell. The advantage of shar over ar is that shar
archives can be read on almost any UNIX system, whereas numerous, incompatible
versions of ar are in widespread use. Extracting the files from a shell
archive requires that sed be accessible.
#sherver
Command: sherver - shell server
Syntax: sherver port
Flags: (none)
Example: sherver machine1 # Start a sherver listening to port
The rsh command does its remote execution by doing a remote procedure call
to some sherver. The sherver executes the command and then exits. Usually a
master will be running to make a new one. Because shervers get their input
from a pipe, remote execution cannot handle signals and CTRL-D, because they
cannot be sent down a pipe.
#size
Command: size - print text, data, and bss size of a program
Syntax: size [file] ...
Flags: (none)
Example: size file # Print the size of file
The text, data, bss, and total sizes for each argument are printed. If no
arguments are present, a.out is assumed. The amount of memory available for
combined stack and data segment growth is printed in the column ``stack.'' This
is the value manipulated by the chmem command. The total amount of memory
allocated to the program when it is loaded is listed under ``memory.'' This
value is just the sum of the other four columns.
#sleep
Command: sleep - suspend execution for a given number of seconds
Syntax: sleep seconds
Flags: (none)
Example: sleep 10 # Suspend execution for 10 sec.
The caller is suspended for the indicated number of seconds. This command
is typically used in shell scripts.
#sort
Command: sort - sort a file of ASCII lines
Syntax: sort [-bcdfimnru] [-tx] [-o name] [+pos1] [-pos2] file ...
Flags: -b Skip leading blanks when making comparisons
-c Check to see if a file is sorted
-d Dictionary order: ignore punctuation
-f Fold upper case onto lower case
-i Ignore nonASCII characters
-m Merge presorted files
-n Numeric sort order
-o Next argument is output file
-r Reverse the sort order
-t Following character is field separator
-u Unique mode (delete duplicate lines)
Examples: sort -nr file # Sort keys numerically, reversed
sort +2 -4 file # Sort using fields 2 and 3 as key
sort +2 -t: -o out # Field separator is :
sort +.3 -.6 # Characters 3 through 5 form the key
Sort sorts one or more files. If no files are specified, stdin is sorted.
Output is written on standard output, unless -o is specified. The options
+pos1 -pos2 use only fields pos1 up to but not including pos2 as the sort key,
where a field is a string of characters delimited by spaces and tabs, unless a
different field delimiter is specified with -t. Both pos1 and pos2 have the
form m.n where m tells the number of fields and n tells the number of charac-
ters. Either m or n may be omitted.
#spell
Command: spell - print all words in a file not present in the dictionary
Syntax: spell file
Flags: (none)
Example: spell document # Print the spelling errors on stdout
Spell is the MINIX spelling checker. It is actually a short shell script.
First, the program prep strips off the roff, nroff, and troff control lines,
and the punctuation, and lists each word on a separate line. These words are
then sorted. The resulting output is then compared to the dictionary. Words
present in the file but not present in the dictionary are listed. The diction-
ary should be located in /usr/lib/dictionary.
#split
Command: split - split a large file into several smaller files
Syntax: split [-n] [file [prefix]]
Flags: -n Number of lines per piece (default: 1000)
Examples: split -200 file # Split file into pieces of 200 lines each
split file z # Split file into zaa, zab, etc.
Split reads file and writes it out in n-line pieces. By default, the pieces
are called xaa, xab, etc. The optional second argument can be used to provide
an alternative prefix for the output file names.
#strings
Command: strings - print all the strings in a binary file
strings file ...
Flags: - search whole file, not just data seg
-o Print octal offset of each string
-n N is minimum length string (default = 4)
Examples: strings -5 a.out # Print the strings > 4 chars in a.out
strings - /bin/sh # Search entire shell file (text and data)
Strings looks for sequences of ASCII characters followed by a zero byte.
These are usually strings. This program is typically used to help identify
unknown binary programs
#strip
Command: strip - remove symbol table from executable file
Syntax: strip [file] ...
Flags: (none)
Example: strip a.out # Remove symbols from a.out
For each file argument, strip removes the symbol table. Strip makes a copy
of the file being stripped, so links are lost.
#stty
Command: stty - set terminal parameters
Syntax: stty [option ...]
Flags: (none)
Examples: stty -echo # Suppress echoing of input
stty erase # # Set the erase character to #
When given no arguments, stty prints the current terminal parameters. It
can also be used to set the parameters, as follows:
cbreak - Enter cbreak mode; erase and kill disabled
echo - Echo input on the terminal
nl - Accept only line feed to end lines
raw - Enter raw mode; no input processing at all
tabs - Output tabs (do not expand to spaces)
erase c - Set erase character (initially backspace)
int c - Set interrupt (SIGINT) character (initially DEL)
kill c - Set kill line character (initially @)
quit c - Set quit (SIGQUIT) character (initially CTRL-\)
default - Set options back to original values
The first five options may be prefixed by - as in -tabs to turn the option off.
The next four options each have a single character parameter separated by a
space from the option. The default option sets the mode and the four settable
characters back to the values they had when the system was booted. It is use-
ful when a rogue program has messed them up.
#su
Command: su - temporarily log in as super-user or another user
Syntax: su [name]
Flags: (none)
Examples: su # Become super-user
su ast # Become ast
Su can be used to temporarily login as another user. It prompts for the
super-user password. If the correct password is entered, su creates a shell
with the desired uid. If no name is specified, root is assumed. To exit the
temporary shell, type CTRL-D.
#sum
Command: sum - compute the checksum and block count of a file
Syntax: sum file
Flags: (none)
Examples: sum /user/ast/xyz # Checksum /user/ast/xyz
Sum computes the checksum of one or more files. It is most often used to
see if a file copied from another machine has been correctly received. This
program works best when both machines use the same checksum algorithm.
#svc
Command: svc - shell version control system
Syntax: ci [-l] [-u] file
co [-l] [-r rev] file
svc file
Flags: -l For ci, checkin, checkout again, and lock file
-l For ci, checkout file and then lock the archive
-u After checking in, do not delete the file
-r Check out revision rev instead most recent revision
Examples: ci -u file # Check in file
co -l file # Check out file and lock archive
co -r 2 file # Check out version 2
Svc is the Shell Version Control system, patterned on RCS. It maintains a
sequence of versions in archive files, so that new versions can be checked in
(added to the archive), and old versions can be checked out (made available).
To create an archive for file, check it in with the -u flag. This action will
prompt for a log message and then create an archive called file,S in the
current directory, or in the subdirectory SVC if it exists. The file will not
be deleted, but will be made unwritable.
To update the file, check it out with the -l flag. Then modify it, and
check it back in, giving a new message when prompted. After this process has
been repeated many times, the archive will contain the entire history. Any
version can be checked out using the -r flag. To get a printout of the his-
tory, use svclog.
#sync
Command: sync - flush the cache to disk
Syntax: sync
Flags: (none)
Example: sync # Write out all modified cache blocks
MINIX maintains a cache of recently used disk blocks. The sync command
writes any modified cache blocks back to the disk. This is essential before
stopping the system, and should be done before running any a.out program that
might crash the system.
#sz
Command: sz - send a file using the zmodem protocol
Syntax: sz [-+LNbdefnopqruvy] [-ci command] [-Ll n] [-t timeout]
Flags: -+ Append to an existing file
-L Use n-byte packets
-N Overwrite if source is newer/longer
-b Binary file
-c Send command for execution
-d Convert dot to slash in names
-e Escape for all control characters
-f Send full path name
-i Send command and return immediately
-l Flow control every n packets
-n Overwrite destination if source is newer
-o Use old (16-bit) checksum
-p Protect file if it already exists
-q Quiet; opposite of verbose
-r Resume interrupt file transfer
-t Set timeout in tenths of a second
-u Unlink file after successful transmission
-v Verbose; opposite of quiet
-y Yes, clobber existing files
Examples: sz file </dev/tty1 >/dev/tty1# Send file
Sz is a program that sends a file sent from another computer using the zmo-
dem protocol. It is a highly complex program. See the /usr/doc/sz.doc and
/usr/doc/rz.doc files for more information.
#tail
Command: tail - print the last few lines of a file
Syntax: tail [-n] [file] ...
Flags: -n How many lines to print
Examples: tail -6 # Print last 6 lines of stdin
tail -1 file1 file2 # Print last line of two files
The last few lines of one or more files are printed. The default count is
10 lines. The default file is stdin.
#tar
Command: tar - tape archiver
Syntax: tar [cxtv] tarfile file ...
Flags: -F Force tar to continue after an error
-c Create a new archive
-o Use the uid/gid of the extractor
-t Print a table listing the archive's contents
-v Verbose mode-tell what is going on as it happens
-x The named files are extracted from the archive
Examples: tar c /dev/fd1 file1 file2 # Create a two-file archive
tar xv /dev/fd1 file1 file2 # Extract two files from the archive
(cd src; tar c -) | (cd dest; tar x -)# Move src tree to dest
Tar is an archiver in the style of the standard tape archiver, except that
it does not use tape. It's primary advantage over ar is that the tar format is
somewhat more standardized than the ar format, making it theoretically possible
to transport MINIX files to another computer, but do not bet on it. If the
target machine runs MS-DOS, try doswrite.
#tee
Command: tee - divert stdin to a file
Syntax: tee [-ai] file ...
Flags: -a Append to the files, rather than overwriting
-i Ignore interrupts
Examples: cat file1 file2 | tee x # Save and display two files
pr file | tee x | lpr # Save the output of pr on x
Tee copies stdin to standard output. It also makes copies on all the files
listed as arguments.
#term
Command: term - turn PC into a dumb terminal
Syntax: term [baudrate] [parity] [bits_per_character]
Flags: (none)
Examples: term 2400 # Talk to modem at 2400 baud
term 1200 7 even # 1200 baud, 7 bits/char, even parity
term 8 9600 # 9600 baud, 8 bits/char, no parity
Term allows MINIX to talk to a terminal or modem over RS232 port 1. The
program first sets the baudrate, parity and character length, and then forks.
The parent sits in a loop copying from stdin (usually the console's keyboard),
to the terminal or modem (/dev/tty1). The child sits in a loop copying from the
terminal or modem (/dev/tty1) to standard output. Thus when RS232 port 1 is
connected to a modem, every keystroke typed on the keyboard is sent to the
modem, and every character arriving from the modem is displayed. Standard
input and output may be redirected, to provide a primitive file transfer pro-
gram, with no checking. To exit term, hit the middle button on the numeric
pad. Important note: to use term, it is essential that /etc/ttys is configured
so that there is no shell hanging on /dev/tty1. If there is, both the shell and
term will try to read from /dev/tty1, and nothing will work.
#termcap
Command: termcap - print the current termcap entry
Syntax: termcap [type]
Flags: (none)
Example: termcap # Print the termcap entry
Termcap reads the /etc/termcap entry corresponding to the terminal type sup-
plied as the argument. If none is given, the current $TERM is used. It then
prints out all the parameters that apply.
#test
Command: test - test for a condition
Syntax: test expr
Flags: (none)
Example: test -r file # See if file is readable
Test checks to see if files exist, are readable, etc. and returns an exit
status of zero if true and nonzero if false. The legal operators are
-r file true if the file is readable
-w file true if the file is writable
-x file true if the file is executable
-f file true if the file is not a directory
-d file true if the file is a directory
-s file true if the file exists and has a size > 0
-t fd true if file descriptor fd (default 1) is a terminal
-z s true if the string s has zero length
-n s true if the string s has nonzero length
s1 = s2 true if the strings s1 and s2 are identical
s1 != s2 true if the strings s1 and s2 are different
m -eq m true if the integers m and n are numerically equal
The operators -gt, -ge, -ne, -le, -lt may be used as well These operands may be
combined with -a (Boolean and), -o (Boolean or), ! (negation). The priority of
-a is higher than that of -o. Parentheses are permitted, but must be escaped to
keep the shell from trying to interpret them.
#time
Command: time - report how long a command takes
Syntax: time command
Flags: (none)
Examples: time a.out # Report how long a.out takes
time ls -l *.c # Report how long ls takes
The command is executed and the real time, user time, and system time (in
hours, minutes, and seconds) are printed.
#to
Command: to - output half of a connection
Syntax: to port
Flags: (none)
Example: cat f1 f2 | to mach4 # Send the catted files to port
To and from are used together to provide connection-oriented service. On
the sending machine, the last member of a pipeline is to port. On the receiving
machine, the first member of a pipe line is from port. The net result is that
the output of the sending pipeline goes into the input of the receiving pipe-
line, making pipelines work across the network. As a simple example, consider:
on machine1: cat f1 f2 | to Johnny
on machine2: from Johnny | sort >x
The effect of these two commands is that the files f1 and f2 are concatenated,
transferred to machine 2, and sorted their, with the output going to a file x
on machine 2. The string Johnny is used by the transaction system to identify
which sender goes with which receiver; any unique string can be used.
#touch
Command: touch - update a file's time of last modification
Syntax: touch [-c] file ...
Flags: -c Do not create the file
Example: touch *.h # Make the .h files look recent
The time of last modification is set to the current time. This command is
mostly used to trick make into thinking that a file is more recent than it
really is. If the file being touched does not exist, it is created, unless the
-c flag is present.
#tr
Command: tr - translate character codes
Syntax: tr [-cds] [string1] [string2]
Flags: -c Complement the set of characters in string1
-d Delete all characters specified in string1
-s Squeeze all runs of characters in string1 to one character
Examples: tr ''[a-z]'' ''[A-Z]'' <x >y # Convert upper case to lower case
tr -d ''0123456789'' <f1 >f2 # Delete all digits from f1
Tr performs simple character translation. When no flag is specified, each
character in string1 is mapped onto the corresponding character in string2.
#traverse
Command: traverse - print directory tree under the named directory
Syntax: traverse dir
Flags: (none)
Example: traverse . # Print tree starting at working dir
Traverse prints the tree structure starting at the named directory. All the
subdirectories are listed, with the depth shown by indentation.
#treecmp
Command: treecmp - recursively list differences in two directory trees
Syntax: treecmp [-v] dir1 dir2
Flags: -v (verbose) list all directories processed
Example: treecmp -v /usr/ast/V1 /usr/ast/V2# Compare two trees
Treecmp recursively descends the directory tree of its first argument and
compares all files to those at the corresponding position in the second argu-
ment. If the two trees are identical, i.e., all the corresponding directories
and files are the same, there is no output. Otherwise, a list of files missing
from one of the trees or present in both but whose contents are not identical
in both are printed.
#true
Command: true - exit with the value true
Syntax: true
Flags: (none)
Example: while true # List the directory until DEL is hit
do ls -l
done
This command returns the value true. It is used for shell programming.
#tset
Command: tset - set the $TERM variable
Syntax: tset [device]
Flags: (none)
Example: eval `tset` # Set TERM
Tset is used almost exclusively to set the shell variable TERM from inside
profiles. If an argument is supplied, that is used as the value of TERM. Oth-
erwise it looks in /etc/ttytype.
#tsort
Command: tsort - topological sort
Syntax: tsort file
Flags: (none)
Example: ar cr libc.a `lorder *.s | tsort`# Build library
Tsort accepts a file of lines containing ordered pairs and builds a total
ordering from the partial orderings.
#ttt
Command: ttt - tic tac toe
Syntax: ttt
Flags: (none)
Example: ttt # Start the game
This program allows the user to engage in a game of tic tac toe (noughts and
crosses) with the computer. The program uses the alpha-beta algorithm, so the
user had better be sharp.
#tty
Command: tty - print the device name of this tty
Syntax: tty
Flags: -s Silent mode (return status only)
Example: tty # Print the tty name
Print the name of the controlling tty
#umount
Command: umount - unmount a mounted file system
Syntax: /etc/umount special
Flags: (none)
Example: /etc/umount /dev/fd1 # Unmount floppy disk 1
A mounted file system is unmounted after the cache has been flushed to disk.
A floppy disk should never be removed while it is mounted. If this happens,
and is discovered before another floppy disk is inserted, the original one can
be replaced without harm. Attempts to unmount a file system holding working
directories or open files will be rejected with a ``device busy'' message.
#unexpand
Command: unexpand - convert spaces to tabs
Syntax: unexpand [-a]
Flags: -a All spaces are unexpanded
Example: unexpand oldfile >newfile # Convert leading spaces to tabs
Unexpand replaces spaces in the named files with tabs. If no files are
listed, stdin is given. The -a flag is used to force all sequences of spaces
to be expanded, instead of just leading spaces (the default).
#uniq
Command: uniq - delete consecutive identical lines in a file
Syntax: uniq [-cdu] [+n] [-n] [input [output]]
Flags: -c Give count of identical lines in the input
-d Only duplicate lines are written to output
-u Only unique lines are written to output
Examples: uniq +2 file # Ignore first 2 fields when comparing
uniq -d inf outf # Write duplicate lines to outf
Uniq examines a file for consecutive lines that are identical. All but
duplicate entries are deleted, and the file is written to output. The +n
option skips the first n fields, where a field is defined as a run of charac-
ters separated by white space. The -n option skips the first n spaces. Fields
are skipped first.
#update
Command: update - periodically write the buffer cache to disk
Syntax: /etc/update
Flags: (none)
Example: /etc/update & # Start a process that flushes the cache
When the system is booted, update is started up in the background from
/etc/rc to issue a SYNC system call every 30 sec.
#users
Command: users - list the logged-in users
Syntax: users
Flags: (none)
Example: users # list the users
Users prints a single line of text containing the names of all the currently
logged-in users.
#uud
Command: uud - decode a binary file encoded with uue
Syntax: uud [-n] [-s srcdir/] [-n dstdir/] file
Flags: -n Do not verify checksums
-s Name of directory where .uue file is
-t Name of directory where output goes
Examples: uud file.uue # Re-create the original file
uud - <file.uue # The - means use stdin
Uud decodes a file encoded with uue or UNIX uuencode. The decoded file is
given the name that the original file had. The name information is part of the
encoded file. Mail headers and other junk before the encoded file are skipped.
#uue
Command: uue - encode a binary file to ASCII (e.g., for mailing)
Syntax: uue [-n] file [-]
Flags: -n Do not verify checksums
-n How many lines to put in each file
Examples: uue file # Encode file to file.uue
uue file - >x # Encode file and write on stdout
uue -800 file # Output on file.uaa, file.uab etc.
Uuuencode is a famous program that converts an arbitrary (usually binary)
file to an encoding using only 64 ASCII characters. Uudecode converts it back
to the original file. The uue and uud programs are the MINIX versions of these
programs, and are compatible with the UNIX ones. The files produced can even
be sent successfully over BITNET, which is notorious for mangling files. It is
possible to have uue automatically split the encoded file up into chunks small
enough to fit into mail messages. The output files then get the suffixes .uaa,
.uab, etc., instead of .uue. When uud is given file.uaa to decode, it automat-
ically includes the subsequent pieces. The encoding takes 3 bytes (24 bits)
from the input file and renders it as 4 bytes in the output file.
#vol
Command: vol - split stdin into diskette-sized volumes
Syntax: vol [-u] size block_special
Flags: -u Unsave from diskettes
Examples: tar c - . | vol 360 /dev/fd0 # Prompt for disk every 360K
vol -u 360 /dev/fd0 | tar x - # Restore a saved file system
It occasionally happens that a program generates an output stream intended
for diskette but the stream is to large to fit on one diskette. Vol is a pro-
gram that accepts such a stream, and pauses every n blocks to request a new
diskette to be inserted. This makes it possible to save arbitrarily long
streams on a series of diskettes, as shown in the examples above.
#wc
Command: wc - count characters, words, and lines in a file
Syntax: wc [-clw] file ...
Flags: -c Print character count
-l Print line count
-w Print word count
Examples: wc file1 file2 # Print all three counts for both files
wc -l file # Print line count only
Wc reads each argument and computes the number of characters, words and
lines it contains. A word is delimited by white space (space, tab, or line
feed). If no flags are present, all three counts are printed.
#whatsnew
Command: whatsnew - print a newly modified file, marking changes
Syntax: whatsnew [-n] file.c file.c.cdif
Flags: -n Output line length
Examples: whatsnew file.c file.c.cdif # Print file.c with changes marked
whatsnew -70 file.c file.c.cdif# Same as above, but with 70 column line
It commonly occurs that cdifs are posted to USENET. After installing a cdif
file, it is sometimes desirable to print out the new file, with the changes
marked on it. Whatsnew does precisely this, with the changes + and ! printed
in the right-hand margin.
#whereis
Command: whereis - examine system directories for a given file
Syntax: whereis file
Flags: (none)
Example: whereis stat.h # Prints: /usr/include/sys/stat.h
Whereis searches a fixed set of system directories, /bin, /lib, /usr/bin,
and others, and prints all occurrences of the argument name in any of them.
#which
Command: which - examine $PATH to see which file will be executed
Syntax: which name
Flags: (none)
Example: which a.out # Tells which a.out will be executed
The $PATH shell variable controls the MINIX search rules. If a command a.out
is given, the shell first tries to find an executable file in the working
directory. If that fails, it looks in various system directories, such as /bin
and /usr/bin. The which command makes the same search and gives the absolute
path of the program that will be chosen, followed by other occurrences of the
file name along the path.
#who
Command: who - print list of currently logged in users
Syntax: who [file]
Flags: (none)
Example: who # Print user names, terminals and times
Who prints a list of currently logged in users. For each one, the user
name, terminal, and login time is printed. This program gets its information
from the file /usr/adm/wtmp, which is updated by init and login. If the file
does not exist, neither of these will create it, and who will not work. Note
that if you decide to create an empty /usr/adm/wtmp to enable the login
accounting, it will grow forever and eventually fill up your disk unless you
manually truncate it from time to time. If an optional file name is provided,
the logins in that file will be printed.
#whoami
Command: whoami - print current user name
Syntax: whoami
Flags: (none)
Example: whoami # Print user name
In case you forget who you are logged in as, whoami will tell you. If you
use su to become somebody else, whoami will give the current effective user.
#width
Command: width - force all the lines of a file to a given width
Syntax: width [-n [ infile [outfile] ]
Flags: -n Outline line size
Examples: width -60 x y # Copy x to y, force lines to 60 cols
width x # Copy default (80) column lines to stdout
The input file is copied to the output file. All lines are forced to a
given size (default: 80 columns) by padding with spaces or truncating. Tabs
are expanded to spaces.
#write
Command: write - send a message to a logged-in user
Syntax: write [cv] user [tty]
Flags: -c Use cbreak mode
-v Verbose mode
Examples: write ast # Send a message to ast
write ast tty1 # Send a message to ast on tty0
Write lets a user send messages to another logged-in user. Lines typed by
the user appear on the other user's screen a line at a time (a character at a
time in the case of cbreak mode). The file /usr/adm/wtmp is searched to deter-
mine which tty to send to. If the user is logged onto more than one terminal,
the tty argument selects the terminal. Type CTRL- D to terminate the command.
Use ! as a shell escape.