shell - Grep command Linux ordering of source string and target string -


grep command syntax as:

grep "literal_string" filename --> search string in filename.

so assuming order of 

-- keyword(grep) --> string searched --> filename/source string , command interpreted left right.

my question how commands such got processed:

ps -ef | grep rman

do order optional?
how grep able know source on left , not on right? or missing here.

when using unix pipes, system commands take output previous command (to left of pipe ) , pass output onto command right of pipe.

the order important when using grep or without pipe.

thus

grep doberman /file/about/dogs

is same as

cat /file/about/dogs | grep doberman

see pipes on http://linuxcommand.org/lts0060.php more information.


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