in reply to dynamic zcat and grep

What Unix and Perl are you running? Just curious.

I was able to get this to work in two ways:
  1. I can only use zcat on .Z files, therefore, I used gunzip -c.
  2. I created a .Z file via compress and used zcat as you have.

Does zcat -h give you any further information?

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Re^2: dynamic zcat and grep
by thor (Priest) on Mar 22, 2006 at 00:33 UTC
    On some systems, gunzip -c and zcat are identical. 
    thulben@alpha:~
17 $ md5sum /bin/gzip /bin/zcat /bin/gunzip
57cd8cdf42fbda6e0a1f5e17ac986b4f  /bin/gzip
57cd8cdf42fbda6e0a1f5e17ac986b4f  /bin/zcat
57cd8cdf42fbda6e0a1f5e17ac986b4f  /bin/gunzip

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    The executable is one of those "magic" ones that recognizes how it was called and alters its behavior appropriately.

    thor

    The only easy day was yesterday

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Re^2: dynamic zcat and grep
by clmcshque (Initiate) on Mar 21, 2006 at 23:50 UTC
    Thanks for the reply. I'm using - perl, v5.8.7 built for i686-linux Red Hat Enterprise zcat works for me when I enter it via the command line, not when it is in a perl script. gunzip -c gives the same errors. When I use single quotes: 
    gunzip: compressed data not read from a terminal. Use -f to force deco
+mpression.
For help, type: gunzip -h

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    When I use double quotes: 
     ERROR - Could not open log.gz

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      Since you are on a Red Hat machine anyway, you can save yourself a lot of time just by using 'zgrep'.

      We're not surrounded, we're in a target-rich environment!
[reply]
        Thanks for the reply. zgrep works great on the command line, but how do I get it to work within my script? Could I do the following: (I would try it but don't have access to the system right now) 
        $grep = /something/;
$gzfile = file.gz;
open OUTPUT "zgrep $grep $gzfile |";

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      You may be able to get a better idea of what is going wrong if you include $! in your error message. This is the variable in which Perl stores the O/S error message when things like open fail, e.g.

      $fn = "non_existant_file";
open IN, "<$fn" or die "open: $fn: $!\n";

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      would error with

      open: non_existant_file: no such file or directory

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      Cheers,

      JohnGG

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