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Full Discussion: what are parent and child processes all about?
Top Forums UNIX for Dummies Questions & Answers what are parent and child processes all about? Post 20474 by Kelam_Magnus on Friday 26th of April 2002 03:53:55 PM
Old 04-26-2002
Good example.
When you use a command like grep or find, they kick off subprocesses (children processes) that actually do the work.

EXAMPLE #1
The parent ( the command that you typed.) "find . -name somefile -print " kicks off subprocesses that actually go out and search for the file that you specified. When they are done they report back to the find command.

EXAMPLE #2
Using grep if you are trying to do something like matching a pattern(s) in a file to print out the lines.

cat filename|grep patterna

This command will actually spawn 2 processes. The cat command, the parent, and the grep command, the child. When the child (grep) finishes it returns to the parent (cat) with the result.

Example #3
Do a ps -aef |grep sh" to find your telnet session. Find your login and do a ps -aef |grep on that PID. All of your commands are technically children of your telnet session as you will see.
 

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LEARN ABOUT POSIX

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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