odin@ucscb.UCSC.EDU (Jon Granrose) (12/15/89)
I am looking for a program that will cat a file backwards. Not with all the letters reversed but one that prints the last line, then the second to last line, 3 from the last line, etc.) If it doesn't exist then I will write my own but I thought I'd ask first. Thanks Jon -- _____________________________________________________________________________ |Jon Granrose |ARPA: odin@ucscb.UCSC.EDU jonathan@sco.com | // Only | |Cowell College, UCSC| 74036.3241@compuserve.com |\X/ Amiga!| |Santa Cruz, CA 95064|UUCP:..!ucbvax!ucscc!ucscb!odin Bitnet:odin@ucscb.bitnet| | "Remember! No matter where you go, there you are." - B. Banzai | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
falk@peregrine.Sun.COM (Ed Falk) (12/16/89)
> >I am looking for a program that will cat a file backwards. Not with all the >letters reversed but one that prints the last line, then the second to last >line, 3 from the last line, etc.) If it doesn't exist then I will write my >own but I thought I'd ask first. The unix tail(1) command will do it.
karl@MorningStar.Com (Karl Fox) (12/16/89)
In article <6488@lindy.Stanford.EDU> odin@ucscb.UCSC.EDU (Jon Granrose) writes:
I am looking for a program that will cat a file backwards. Not with all the
letters reversed but one that prints the last line, then the second to last
line, 3 from the last line, etc.) If it doesn't exist then I will write my
own but I thought I'd ask first.
Try this:
#!/bin/sh
grep -n "^" $* | sort -rn -t: | cut -d: -f2-
--
Karl Fox, Morning Star Technologies karl@MorningStar.COMbill@twwells.com (T. William Wells) (12/16/89)
In article <6488@lindy.Stanford.EDU> odin@ucscb.UCSC.EDU (Jon Granrose) writes:
: I am looking for a program that will cat a file backwards. Not with all the
: letters reversed but one that prints the last line, then the second to last
: line, 3 from the last line, etc.) If it doesn't exist then I will write my
: own but I thought I'd ask first.
Try: nl | sort -nr | cut (you figure the arguments). I would not
be surprised to find that this is as fast as a "tailored" program.
(Why? Because the disk access pattern of the sort *might* be
better than that of a file reverser.)
---
Bill { uunet | novavax | ankh | sunvice } !twwells!bill
bill@twwells.com" Maynard) (12/16/89)
In article <6488@lindy.Stanford.EDU> odin@ucscb.UCSC.EDU (Jon Granrose) writes: >I am looking for a program that will cat a file backwards. Not with all the >letters reversed but one that prints the last line, then the second to last >line, 3 from the last line, etc.) If it doesn't exist then I will write my >own but I thought I'd ask first. It's probably pretty simple to do in C, but here's a quick and dirty in awk I use to insure that my disks get unmounted in the reverse order of being mounted: awk '{ lines[NR] = $0 } END { for(i=NR; i>=1; i--) print lines[i]; }' <file It's not the fastest in the world, and it's limited by awk's available memory, but it does the job... -- Jay Maynard, EMT-P, K5ZC, PP-ASEL | Never ascribe to malice that which can jay@splut.conmicro.com (eieio)| adequately be explained by stupidity. {attctc,bellcore}!texbell!splut!jay +---------------------------------------- Here come Democrats...here come Democrats...throwing money a-way...
merlyn@iwarp.intel.com (Randal Schwartz) (12/16/89)
In article <6488@lindy.Stanford.EDU>, odin@ucscb (Jon Granrose) writes: | I am looking for a program that will cat a file backwards. Not with all the | letters reversed but one that prints the last line, then the second to last | line, 3 from the last line, etc.) If it doesn't exist then I will write my | own but I thought I'd ask first. Don't write your own... get Perl... perl -e 'print reverse(<>);' Simple, eh? Just another Perl hacker, -- /== Randal L. Schwartz, Stonehenge Consulting Services (503)777-0095 ====\ | on contract to Intel's iWarp project, Hillsboro, Oregon, USA, Sol III | | merlyn@iwarp.intel.com ...!uunet!iwarp.intel.com!merlyn | \== Cute Quote: "Welcome to Oregon... Home of the California Raisins!" ==/
irwin@m.cs.uiuc.edu (12/16/89)
/* Written 2:12 am Dec 15, 1989 by odin@ucscb.UCSC.EDU in m.cs.uiuc.edu:comp.sources.wanted */ /* ---------- "Backwards cat" ---------- */ >I am looking for a program that will cat a file backwards. Not with all the >letters reversed but one that prints the last line, then the second to last >line, 3 from the last line, etc.) If it doesn't exist then I will write my >own but I thought I'd ask first. >Thanks >Jon -- _____________________________________________________________________________ |Jon Granrose |ARPA: odin@ucscb.UCSC.EDU jonathan@sco.com | // Only | |Cowell College, UCSC| 74036.3241@compuserve.com |\X/ Amiga!| |Santa Cruz, CA 95064|UUCP:..!ucbvax!ucscc!ucscb!odin Bitnet:odin@ucscb.bitnet| | "Remember! No matter where you go, there you are." - B. Banzai | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /* End of text from m.cs.uiuc.edu:comp.sources.wanted */ It sounds like you could use the LESS utility to do what you want. It is mentioned in this forum in another thread. Al Irwin Univ of Illinois Dept of Comp Sci irwin@m.cs.uiuc.edu
tomm@voodoo.UUCP (Tom Mackey) (12/16/89)
In article <6488@lindy.Stanford.EDU> odin@ucscb.UCSC.EDU (Jon Granrose) writes: >I am looking for a program that will cat a file backwards. Not with all the >letters reversed but one that prints the last line, then the second to last >line, 3 from the last line, etc.) If it doesn't exist then I will write my >own but I thought I'd ask first. >Thanks >Jon >-- > _____________________________________________________________________________ >|Jon Granrose |ARPA: odin@ucscb.UCSC.EDU jonathan@sco.com | // Only | >|Cowell College, UCSC| 74036.3241@compuserve.com |\X/ Amiga!| >|Santa Cruz, CA 95064|UUCP:..!ucbvax!ucscc!ucscb!odin Bitnet:odin@ucscb.bitnet| >| "Remember! No matter where you go, there you are." - B. Banzai | >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I am going to post the source and manpage for tac to alt.sources. I suspect that many will send you the source, but I haven't seen it posted lately. If you don't get alt.sources, and still want it, let me know and I'll try exercising our mailer. -- Tom Mackey (206) 234-7767 (wk) Boeing Computer Services ....uw-beaver!ssc-vax!voodoo!tomm M/S 6M-17, P.O. Box 24346, Seattle, WA 98124-0346
6600pete@hub.UUCP (12/16/89)
From article <6488@lindy.Stanford.EDU>, by odin@ucscb.UCSC.EDU (Jon Granrose): > I am looking for a program that will cat a file backwards. Not with all the > letters reversed but one that prints the last line, then the second to last > line, 3 from the last line, etc.) If it doesn't exist then I will write my > own but I thought I'd ask first. ...and the fourth answer... TAIL(1) USER COMMANDS TAIL(1) NAME tail - display the last part of a file SYNOPSIS tail +|-number [ lbc ] [ fr ] [ filename ] OPTIONS r Copy lines from the end of the file in reverse order. The default for r is to print the entire file in reverse order. ------------------------------------------------------------------------------- Pete Gontier | InterNet: 6600pete@ucsbuxa.ucsb.edu, BitNet: 6600pete@ucsbuxa Editor, Macker | Online Macintosh Programming Journal; mail for subscription Hire this kid | Mac, DOS, C, Pascal, asm, excellent communication skills
morfeq@boulder.Colorado.EDU (Ali H. Morfeq) (12/16/89)
there is procedure written in C in the book :
"Advanced Unix programming' by Marc J. Rochkind, Prentice-Hall
1985.
It is in section 2.11. it is exactley what you described. It takes
a file name and output the file in reverse order of lines.
for example: if file : dog
bites
man
then it will produce:
man
bites
dog
morfeq@boulder.colorado.eduken@cs.rochester.edu (Ken Yap) (12/16/89)
So does a backwards cat go "woaim"? Sorry, couldn't resist. :-)
roy@comcon.UUCP (Roy M. Silvernail) (12/16/89)
In article <3324@hub.UUCP>, 6600pete@hub.UUCP writes: > From article <6488@lindy.Stanford.EDU>, by odin@ucscb.UCSC.EDU (Jon Granrose): > > I am looking for a program that will cat a file backwards. Not with all the > > letters reversed but one that prints the last line, then the second to last > > line, 3 from the last line, etc.) If it doesn't exist then I will write my > > own but I thought I'd ask first. > > ...and the fourth answer... > > TAIL(1) USER COMMANDS TAIL(1) > Hmmm... at this site, not quite: tail -r data usage: tail [+/-[n][lbc][f]] [file] man tail man: tail not found ah, well.... I don't have to reverse files very often:-) -- _R_o_y _M_. _S_i_l_v_e_r_n_a_i_l | UUCP: uunet!comcon!roy | "No, I don't live in an igloo!" [ah, but it's my account... of course I opine!] -Sourdough's riposte SnailMail: P.O. Box 210856, Anchorage, Alaska, 99521-0856, U.S.A., Earth, etc.
tchrist@convex.COM (Tom Christiansen) (12/17/89)
In article <5360@omepd.UUCP> merlyn@iwarp.intel.com (Randal Schwartz) writes: |In article <6488@lindy.Stanford.EDU>, odin@ucscb (Jon Granrose) writes: || I am looking for a program that will cat a file backwards. Not with all the || letters reversed but one that prints the last line, then the second to last || line, 3 from the last line, etc.) If it doesn't exist then I will write my || own but I thought I'd ask first. | |Don't write your own... get Perl... |perl -e 'print reverse(<>);' |Simple, eh? My first reaction at the original posting was to use "tail -r", but I like Randal's solution a good deal anyway. You'd think a dedicated utility like tail would be more efficient than a general purpose interpreted language like perl (or awk, which is less general-purpose), but much to my surprise, I found this (on a minimally configured CONVEX C1): % wc /etc/termcap 2235 8179 102598 /etc/termcap % time tail -r /etc/termcap > /dev/null 1.4u 0.3s 0:01 93% 0+18k 0+0io 67pf+0w % time perl -e 'print reverse(<>);' /etc/termcap > /dev/null 0.7u 0.3s 0:01 91% 0+25k 0+5io 127pf+0w I also tried Jay Maynards awk solution: % time awk '{ lines[NR] = $0 } END { for(i=NR; i>=1; i--) print lines[i]; }' < /etc/termcap > /dev/null 9.3u 0.9s 0:12 79% 0+3k 27+0io 95pf+0w % time nawk .... 6.9u 0.8s 0:08 89% 0+4k 39+1io 114pf+0w % time gawk .... 6.6u 1.9s 0:09 86% 0+4k 11+8io 214pf+0w Which is pretty sad performance by my book. --tom Tom Christiansen {uunet,uiucdcs,sun}!convex!tchrist Convex Computer Corporation tchrist@convex.COM "EMACS belongs in <sys/errno.h>: Editor too big!"
emv@math.lsa.umich.edu (Edward Vielmetti) (12/17/89)
I mailed this to Jon but I haven't seen it here yet. 'tac', from 4.3 BSD contrib, author is Jay Lepreau. didn't we have this discussion a few weeks ago? Perhaps this is something for 'Frequently Answered Questions.'. --Ed
guy@auspex.UUCP (Guy Harris) (12/19/89)
>...and the fourth answer...
Which isn't correct:
auspex% tail -r /etc/termcap > /tmp/stuff
auspex% ls -lL /tmp/stuff /etc/termcap
-rw-rw-r-- 1 root 133962 Jul 14 14:39 /etc/termcap
-rw-r--r-- 1 guy 32768 Dec 18 13:01 /tmp/stuff
32768 != 133962. "tail -r" doesn't reverse the *entire* file, just a
chunk at the end, in the UNIX versions I know of:
BUGS
Data for a tail relative to the end of the file is stored in
a buffer, and thus is limited in size.