Shell Programming and Scripting

Linux version : Oracle Linux 6.5
Shell : bash


In the the below text file (someString.text), I want to grep all lines with .sh in it. ie. Only the lines mysript.sh and anotherscript.sh should be returned.
My below attempts failed.
I gather that in regular expression world, dot (.) is the wild card for any single character . So, what is the workaround ?

Code:

$ cat someString.text
/bin/sh
/bin/ssh
korn shell
mysript.sh
anotherscript.sh



$ grep *.sh someString.text
$

$ grep sh someString.text
/bin/sh
/bin/ssh
korn shell
mysript.sh
anotherscript.sh
$
$
$ grep .sh someString.text
/bin/sh
/bin/ssh
korn shell
mysript.sh
anotherscript.sh
$
$
$ grep *sh someString.text
$
$ grep sh someString.text
/bin/sh
/bin/ssh
korn shell
mysript.sh
anotherscript.sh
$

The grep regular expression must be quoted. The dot has a special meaning ("any character") so it must be escaped with a back slash to use its literal meaning. try:

Code:

grep '\.sh$' file

The dollar sign signifies that the match must be at the end of the line.

It might be better to quote the string you are searching for. The version grep *.sh someString.text could yield different results based on other files in the directory because the shell will assum you want to expand the * character to match all files that finish sh, so your command executed could end up being:-

Code:

grep 1sh 2.sh hello.sh my-oh-my.ksh wish someString.text

This would mean it would search for 1sh in all the other files listed, which probably is not what you want.

Additionally, the dot is a special character that matches any single character. That might seem odd, but you might want to match A..B to get A01B, A02B, A17B etc. so to ensure it is the literal character dot, you need to use a backslash \ to escape it.

With quoting, it might help a little, but you need to be clear on what you are searching for, so:-In the latter, the $ in this case marks/anchors the search to the end of line. There could be other cases, such as .sh followed by a space, tab, hash etc., depending on the whole content of your file.


Does this do what you need, or are there other conditions to consider?


Kind regards,
Robin

Another option is to use a literal string match (so the are no special meaning to characters) with the -F parameter. If .sh always only occurs at the end of the line anyway, you could also try:

Code:

grep -F '.sh' file