Write to file using tail -f through a pipe to grep Post: 302497250

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Top Forums UNIX for Dummies Questions & Answers Write to file using tail -f through a pipe to grep Post 302497250 by ndedhia1 on Wednesday 16th of February 2011 04:44:05 PM

02-16-2011

Registered User

Write to file using tail -f through a pipe to grep

Hi -- I'm looking to write to a file after piping output from tail -f through to grep:

#write to a file for all lines with "searchtext" within in error_log:

Expand|Select|Wrap|Line Numbers

tail -f /var/error_log | grep searchtext > output.txt

The above command fails even though the following command::
Expand|Select|Wrap|Line Numbers

tail -f /var/error_log | grep searchtext

does produce output, as expected. Nothing is getting through while redirecting to files after a tail -f... The following work:
Expand|Select|Wrap|Line Numbers

tail -f /var/error_log > output.txt //without grep
tail /var/error_log | grep searchtext > output.txt //without -f

So it's just the combination of grep and tail with specifically the -f (following) option that causes the problem. It would be ideal to be able to do this with a single inline command. Any ideas?

thanks for the help!!

ndedhia1

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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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