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Full Discussion: How to read each file grep a value from that?
Top Forums Shell Programming and Scripting How to read each file grep a value from that? Post 303005811 by Don Cragun on Monday 23rd of October 2017 02:14:16 PM
Old 10-23-2017
If all of the files are in a single directory (not spread out among subdirectories), you could try the following first:
Code:
cd /tmp
grep -FHi 'Calling appalert' *.log

or, if you just want the names of files containing that string (with a case insensitive match):
Code:
cd /tmp
grep -Fli 'Calling appalert' *.log

These might file with "argument list too long" errors depending on how many thousands of files you have, but it is easy to try it. And, if it works, it will hundreds or thousands of times faster that performing a grep on each file individually. If they won't work, you'll know quickly.

Note that I added a -F option to grep. Searching for fixed strings (even if you're doing a case-insensitive match), is faster than going through the extra complexity of matching regular expressions.

If all of the log entries use the same case, dropping the -i option will also make it run faster.
This User Gave Thanks to Don Cragun For This Post:
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LEARN ABOUT V7

zgrep

ZGREP(1)						      General Commands Manual							  ZGREP(1)

NAME

       zgrep - search possibly compressed files for a regular expression

SYNOPSIS

       zgrep [ grep_options ] [ -e ] pattern filename...

DESCRIPTION

       Zgrep  invokes  grep  on  compressed  or  gzipped  files.   These  grep	options  will  cause  zgrep  to  terminate  with  an  error  code:
       (-[drRzZ]|--di*|--exc*|--inc*|--rec*|--nu*).  All other options specified are passed directly to grep.  If no file is specified,  then  the
       standard input is decompressed if necessary and fed to grep.  Otherwise the given files are uncompressed if necessary and fed to grep.

       If the GREP environment variable is set, zgrep uses it as the grep program to be invoked.

EXIT CODE

       2 - An option that is not supported was specified.

AUTHOR

       Charles Levert (charles@comm.polymtl.ca)

SEE ALSO

       grep(1), gzexe(1), gzip(1), zdiff(1), zforce(1), zmore(1), znew(1)

																	  ZGREP(1)
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