Need some grep help, please [Solved]

[satuser083]

I need some help with using grep in a script. In the script I have

arc_src_UUID1=`ls -l /dev/disk/by-label | grep "$arc_src_label"`, where arc_src_label contains e.g. "Abcde"

Grep finds all occurences of "Abcde", including "Abcde", "Abcdef", "Abcdefg", etc., whereas I only want "Abcde". Adding a space to the contents of arc_src_label has no effect (it looks as though grep ignores this space).

In a terminal the following works

ls -l /dev/disk/by-label | grep "Abcde ", i.e. embedding the pattern-string (plus a space) in "" solves the problem - only "Abcde" is found. Since this clearly works, I assume that it's a script-syntax problem.

Can anyone help me out with the correct syntax? Thanks.

[Just17]

Can you not add the space when 'Abcde' is applied to the variable?

arc_src_label="Abcde "

.....  or maybe the  grep  -w  option would do as you want?

grep -w Abcde

[satuser083]

I need some help with using grep in a script. In the script I have

arc_src_UUID1=`ls -l /dev/disk/by-label | grep "$arc_src_label"`, where arc_src_label contains e.g. "Abcde"

Grep finds all occurences of "Abcde", including "Abcde", "Abcdef", "Abcdefg", etc., whereas I only want "Abcde". Adding a space to the contents of arc_src_label has no effect (it looks as though grep ignores this space).

In a terminal the following works

ls -l /dev/disk/by-label | grep "Abcde ", i.e. embedding the pattern-string (plus a space) in "" solves the problem - only "Abcde" is found. Since this clearly works, I assume that it's a script-syntax problem.

Can anyone help me out with the correct syntax? Thanks.

OK, should have looked a bit longer  . The answer I found in a tutorial is:

... grep -w "$arc_src_label"`, although the logic of the -w in this case isn't immediately apparent (not to me, anyway). Important thing, though,  it's working now.

[pags]

I need some help with using grep in a script. In the script I have

arc_src_UUID1=`ls -l /dev/disk/by-label | grep "$arc_src_label"`, where arc_src_label contains e.g. "Abcde"

Grep finds all occurences of "Abcde", including "Abcde", "Abcdef", "Abcdefg", etc., whereas I only want "Abcde". Adding a space to the contents of arc_src_label has no effect (it looks as though grep ignores this space).

In a terminal the following works

ls -l /dev/disk/by-label | grep "Abcde ", i.e. embedding the pattern-string (plus a space) in "" solves the problem - only "Abcde" is found. Since this clearly works, I assume that it's a script-syntax problem.

Can anyone help me out with the correct syntax? Thanks.

OK, should have looked a bit longer  . The answer I found in a tutorial is:

... grep -w "$arc_src_label"`, although the logic of the -w in this case isn't immediately apparent (not to me, anyway). Important thing, though,  it's working now.

From

Code: [Select]

man grep


-w, --word-regexp
              Select  only  those  lines  containing  matches  that  form  whole words.  The test is that the matching
              substring must either be at the beginning of the line, or preceded by a non-word constituent  character.
              Similarly,  it  must  be  either at the end of the line or followed by a non-word constituent character.
              Word-constituent characters are letters, digits, and the underscore.

So, it is only matching when the string you're looking for is a "whole word"

[satuser083]

Thanks, pags, knew the explanation was there somewhere. I was pretty sure there was an option for this, but couldn't find it in the million or so hits I got about grep-syntax  . Thanks, once again