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Full Discussion: help with simple regex expression
Top Forums Shell Programming and Scripting help with simple regex expression Post 302481093 by schms on Thursday 16th of December 2010 03:57:33 PM
Old 12-16-2010
help with simple regex expression
I am trying to grep the following line in a file using a bash shell:

(..)
admin1::14959::::::
(..)

It works with the following expression (as expected)

# cat file | grep ^[a-z0-9]*::
admin1::14959::::::

but it does not work with (not expected)

# cat /etc/shadow | grep ^[a-z0-9]+::

I assume the difference is the + vs. the *. According my
understanding the * matches the preceding character 0 or
more times and the + matches the preceding character 1
or more times. Therefore, the match should be in both cases
"admin1::"

I can not see my mistake. Any ideas ?
 

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LEARN ABOUT PLAN9

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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