quan@hplabsb.HP.COM (Suu Quan) (11/29/89)
How do I write a C-program or shell script that will watch for
the presence of a new file in a certain directory.
Scenario : I expect a file to be sent to me -name possibly unknown- to a
directory (callit /application/inputfile/). Since I do not know when it
will arrive (ftp, rcp ... does not matter), I want to be notified of its
presence as soon as possible but not burn any cpu in the mean time.
I know how to write a shell script will a loop and a sleep a la :
cd /application/inputfile/
while (1)
do
sleep($some)
if [ $(/bin/ls) ] # assume ksh
then
echo there is something in here
else
;
fi
done.
But I would prefer a C-program or a script using a blocking command
Any help is appreciated
--
Suu Quan (TELNET/415) 857-3594 quan@hpcmfs.corp.HP.COM
HEWLETT-PACKARD, Corp Manuf Factory Systems quan@hpcmfs
Palo Alto, CA 94304 suu quan /HP0080/04cpcahil@virtech.uucp (Conor P. Cahill) (11/29/89)
In article <5506@hplabsb.HP.COM>, quan@hplabsb.HP.COM (Suu Quan) writes: > How do I write a C-program or shell script that will watch for > the presence of a new file in a certain directory. [example shell deleted] > But I would prefer a C-program or a script using a blocking command There is no way to sleep on a file being added to a directory. If you can't modify the software that is sending the file (to use some kind of IPC to tell your daemon that the file is there), the next best thing you could do is: set dir mtime var to non zero; set old mtime var to zero; forever loop { if( dir mtime var != old mtime var) { /* The dir has been modified, so look for new stuff...*/ old mtime var = dir mtime var } else { sleep(however long is ok); } stat(dir,to get current dir mtime var) } NOTE-> the code above was just off the top of my head, so there may be a typo, bug, mistake, or other such stuff. This way you are only stating the directory every x seconds (unless there is a file to process) and this shouldn't use up any measurable CPU as long as long as the sleep is > 1 second. -- +-----------------------------------------------------------------------+ | Conor P. Cahill uunet!virtech!cpcahil 703-430-9247 ! | Virtual Technologies Inc., P. O. Box 876, Sterling, VA 22170 | +-----------------------------------------------------------------------+
les@chinet.chi.il.us (Leslie Mikesell) (11/30/89)
In article <5506@hplabsb.HP.COM> quan@hplabsb.HP.COM (Suu Quan) writes: > > How do I write a C-program or shell script that will watch for >the presence of a new file in a certain directory. > >Scenario : I expect a file to be sent to me -name possibly unknown- to a >directory (callit /application/inputfile/). Since I do not know when it >will arrive (ftp, rcp ... does not matter), I want to be notified of its >presence as soon as possible but not burn any cpu in the mean time. The cheapest operation would probably be to stat(2) the directory at some interval, then use opendir(), readdir(), etc. to find the filename when the st_mtime field changes. For a shell approach you will have to read the directory but the (generally) built-in echo command will do it. # cd dir while : do FILES=`echo *` if [ $FILES != "*" ] then # put your notify command here... exit fi sleep 30 done > But I would prefer a C-program or a script using a blocking command > Any help is appreciated That would require some help from the delivery program - for example writing to a FIFO when the delivery is complete. In any case you might need to guard against processing a partial file (i.e. the name has appeared but the writer has not completed its output). Les Mikesell les@chinet.chi.il.us
chris@mimsy.umd.edu (Chris Torek) (11/30/89)
In article <1989Nov29.042955.8217@virtech.uucp> cpcahil@virtech.uucp (Conor P. Cahill) writes: > forever loop ... > stat(dir,to get current dir mtime var) If you open the directory, and use fstat on the resulting descriptor, you will accumulate less system time. Unfortunately, it seems that some Unix systems refuse to let you open a directory these days, so you would need something like fd = open(dir, 0); forever loop ... result = fd >= 0 ? fstat(fd, &st) : stat(dir, &st); if (result < 0) er ror er ror ster ril lize (no points for remembering the source of the `er ror' line :-) ) -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163) Domain: chris@cs.umd.edu Path: uunet!mimsy!chris
ken@wsl.UUCP (Kenneth Woods on wsl) (12/08/89)
----- News saved at 7 Dec 89 23:20:43 GMT >In article <5506@hplabsb.HP.COM>, quan@hplabsb.HP.COM (Suu Quan) writes: >> How do I write a C-program or shell script that will watch for >> the presence of a new file in a certain directory. If you use the C-shell you could try the following command set mail = ( 10 /usr/mail/$LOGNAME certain_directory ) csh will then send you the message "New mail in certain_directory" whenever a file is added or removed from that directory. You can use ls -t or whatever to find the actual name of the file. Newsgroups: comp.unix.questions,hp.unix Subject: Re: how do you watch for an incoming file Summary: Expires: References: <5506@hplabsb.HP.COM> <1989Nov29.042955.8217@virtech.uucp> Sender: Reply-To: ken@wsl.ie (Kenneth Woods on wsl) Followup-To: Distribution: Organization: Workhorse Systems, Dublin, Ireland Keywords: >In article <5506@hplabsb.HP.COM>, quan@hplabsb.HP.COM (Suu Quan) writes: >> How do I write a C-program or shell script that will watch for >> the presence of a new file in a certain directory. If you use the C-shell you could try the following command set mail = ( 10 /usr/mail/$LOGNAME certain_directory ) csh will then send you the message "New mail in certain_directory" whenever a file is added or removed from that directory. You can use ls -t or whatever to find the actual name of the file.