check variable content size in sh script

Teske, Devin Devin.Teske at
Thu May 16 16:06:52 UTC 2013

On May 16, 2013, at 8:28 AM, Tim Daneliuk wrote:

> On 05/16/2013 10:08 AM, Joe wrote:
>> Hello
>> Have script that has max size on content in a variable.
>> How to code size less than 51 characters?
> FOO="Some string you want to check length of"
> FOOLEN=`echo $FOO | wc | awk '{print $3}'`

Uh, without forking to 2 separate programs…


> You can then use $FOOLEN in a conditional.

However, if the OP wanted to actually truncate $FOO to 51 characters:

NEWFOO=$( echo "$FOO" | awk -v max=51 '{print substr($0,0,max)}' )

However, if you want to handle the case of $FOO containing newlines (and you want the newline to count toward the max), then this instead would do the trick:

NEWFOO=$( echo "$FOO" | awk -v max=51 '
		len = length($0)
		max -= len
		print substr($0,0,(max > 0 ? len : max + len))
		if ( max < 0 ) exit
	}' )

$NEWFOO, even if multi-line, will be limited to 51-bytes (adjust max=51 accordingly for other desired-lengths). Newlines are preserved.

Last, but not least, if you want to be able to handle multi-line values but only want to return the first line up-to N bytes (using 51 as the OP used):

NEWFOO=$( echo "$FOO" | awk -v max=51 '{ print substr($0,0,max); exit }' )

If $FOO had multiple lines, $NEWFOO will have only the first line (and it will be truncated to 51 bytes or less).

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