BASH: How to NOT echo to screen with "if echo $x

eur0dad · 07-27-2006, 12:43 PM

if echo $x | grep ".*"; then
...
fi

Is there a way of getting around this type of stuff without actually printing it out to the screen? The user shouldn't be seeing this. I'm trying to test if the string matches the grep regex.

Matir · 07-27-2006, 01:28 PM

Then do:

Code:

if [ $( echo $x | grep -c ".*" ) -gt 0 ]
    then echo "Match found."
fi

raskin · 07-27-2006, 01:31 PM

redirect to /dev/null. Read man bash, maybe?
if echo | grep >/dev/null;

raskin · 07-27-2006, 01:33 PM

By the way, are you checking for empty string? Read man bash on test ( [ ), it has -z and -n flags to do it.

marozsas · 07-27-2006, 01:42 PM

Use the grep's quiet option.

Code:

if echo $x | grep -q ".*"; then
...

spirit receiver · 07-27-2006, 01:48 PM

Note that there's a bash built-in to do this. From "man bash":

Quote:

[[ expression ]]
[...]
An additional binary operator, =~, is available, with the same precedence as == and !=. When it is used, the string to the right of the operator is considered an extended regular expression and matched accordingly (as in regex(3)).

Matir · 07-27-2006, 01:53 PM

Quote:

Originally Posted by spirit receiver

Note that there's a bash built-in to do this. From "man bash":

Ah yes, one of those little known bash tricks.

raskin · 07-27-2006, 02:06 PM

Well, it's non-POSIX!

eur0dad · 07-27-2006, 02:12 PM

Quote:

Originally Posted by spirit receiver

Note that there's a bash built-in to do this. From "man bash":

I originally tried that, but I had to work around it because my version of bash didn't support it.

eur0dad · 07-27-2006, 02:14 PM

Quote:

Originally Posted by marozsas

Use the grep's quiet option.

Code:

if echo $x | grep -q ".*"; then
...

This worked perfectly.