output="$(awk -F',' '/Name/ {print $9}' input.file)"
How do trim leading and trailing whitespace from bash variable called $output? How do I trim trailing whitespace from $output?
You can use sed, awk, cut, tr, and other utilities to remove whitespace from $output.
Sample data
| Tutorial details | |
|---|---|
| Difficulty level | Easy |
| Root privileges | No |
| Requirements | Linux/Unix+Bash/Ksh |
| Est. reading time | N/A |
output=" This is a test"
Use echo statement to display $output:
echo "=${output}="
Sample outputs:
= This is a test=
sed Example
The syntax is:
echo "${output}" | sed -e 's/^[ \t]*//'
Sample outputs:
This is a test
Bash Example
The syntax is to remove leading whitespaces:
${var##*( )}
For example:
# Just remove leading whiltespace #turn it on shopt -s extglob output=" This is a test" output="${output##*( )}" echo "=${output}=" # turn it off shopt -u extglob
Sample outputs:
=This is a test=
To trim leading and trailing whitespace using bash, try:
#turn it on shopt -s extglob output=" This is a test " ### Trim leading whitespaces ### output="${output##*( )}" ### trim trailing whitespaces ## output="${output%%*( )} echo "=${output}=" # turn it off shopt -u extglob
Sample outputs:
=This is a test=
awk Example
The syntax is:
output=" This is a test " echo "=${output}=" ## Use awk to trim leading and trailing whitespace echo "${output}" | awk '{gsub(/^ +| +$/,"")} {print "=" $0 "="}'
Sample outputs:
=This is a test=
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🐧 16 comments so far... add one ↓
🐧 16 comments so far... add one ↓
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check the title it says “While” Spaces
Thanks for the heads up!
I tend to just stick to sed for this typeof thing:
jsoap@nixbox:~$ output=" This is a test " jsoap@nixbox:~$ echo "=${output}=" = This is a test = jsoap@nixbox:~$ output=$( echo "${output}"| sed -e 's/^ *//' -e 's/ *$//' ); jsoap@nixbox:~$ echo "=${output}=" =This is a test= jsoap@nixbox:~$Since a lot of my work needs to live on BSD, AIX and Solaris, as well as on Linux, I tend to script very defensively and portably. It has saved my butt more times than bears mentioning…
If the content is a single line of text, why not just use echo ?
notice there are no double-quotes for the inner $VAR
… slight error …. it should be
This is the BEST site in the world. I can’t tell you how many times I have wound up here to find the answer to my question or problem. Great resource, thanks!!!
Hello..
Could you please help me out….
Here is my scenario:
1. i am listing some of the processes which are active and sending the output to temp.txt.
2. i got many processes, if i want to kill/doing some thing with any inactive process it should throw an error message.
3. how do i work with pattern matching commands in temp.txt?
Please suggest me the better answer..
m=$( echo "${output}" | sed -e "s/^\ *//g" -e "s/\ *$//g") echo "=${m}=" =This is a test=Very helpful. Thanks.
I’m not sure why the examples use extglob in bash. It’s completely unneeded when using the ## or %% operators. ${VAR%% } will remove trailing whitespace, as long as it’s not mixed tabs and spaces.
echo ” blah ” | awk ‘{print $NF }’
You can also pipe to tr this:
"${output##*( )}" output="${output%%*( )}Is this bash version specific ? Any reference for the same ?
Thanks
This is great useful site!!
Thanks!
I extend the ‘Bash Example’ as follows:
useful for whitespaces the ${var##*(tab|space)} form, where the tab is itself, and the space is also itself, it look like ${var##*( | )} or ${var%%( | )} typed in editor.
Thanks, and best regards, Miki
awk ‘{$1=$1};1’