How to Trim White Space from a Variable in Awk

How can I trim white space from a variable in awk?

You're printing the result of the gsub, but gsub does an in-place modify of $2 instead of returning a modified copy. Call gsub, then print:

awk -F\, '{gsub(/[ \t]+$/, "", $2); print $2 ":"}'

Trim leading and trailing spaces from a string in awk

If you want to trim all spaces, only in lines that have a comma, and use awk, then the following will work for you:

awk -F, '/,/{gsub(/ /, "", $0); print} ' input.txt

If you only want to remove spaces in the second column, change the expression to

awk -F, '/,/{gsub(/ /, "", $2); print$1","$2} ' input.txt

Note that gsub substitutes the character in // with the second expression, in the variable that is the third parameter - and does so in-place - in other words, when it's done, the $0 (or $2) has been modified.

Full explanation:

-F,            use comma as field separator 
               (so the thing before the first comma is $1, etc)
/,/            operate only on lines with a comma 
               (this means empty lines are skipped)
gsub(a,b,c)    match the regular expression a, replace it with b, 
               and do all this with the contents of c
print$1","$2   print the contents of field 1, a comma, then field 2
input.txt      use input.txt as the source of lines to process

EDIT I want to point out that @BMW's solution is better, as it actually trims only leading and trailing spaces with two successive gsub commands. Whilst giving credit I will give an explanation of how it works.

gsub(/^[ \t]+/,"",$2);    - starting at the beginning (^) replace all (+ = zero or more, greedy)
                             consecutive tabs and spaces with an empty string
gsub(/[ \t]+$/,"",$2)}    - do the same, but now for all space up to the end of string ($)
1                         - ="true". Shorthand for "use default action", which is print $0
                          - that is, print the entire (modified) line

Trim extra spaces in AWK

For the current example, another option might be to recalculate the text of the input record by first setting the value of line to the input record and then use $1=$1

awk -v line="    foo    bar  " 'END {$0=line; $1=$1; print}' somefile.txt

Output (the quotes are only for clarity that there are no leading or trailing spaces)

"foo bar"

The inner workings how the spaces are removed are described in the comments by Ed Morton:

Setting $0=line or any other change to $0 would trigger the fields being recalculated.

Using $1=$1 triggers the record to be recalculated in as much as it'll be rebuilt from the existing fields thereby stripping leading/trailing white space and replacing every other chain of contiguous white space with a single blank char (assuming the default FS and OFS are used).

removing a space from a string by awk

gsub is your friend. The following command basically does a global substitution of a regular expression (a single space in this case), replacing it with an empty string, on the target $0 (the whole line).

pax> echo "steve john" | awk '{ gsub (" ", "", $0); print}'
stevejohn

You can use any target, including one input by a user:

pax> awk 'BEGIN {getline xyzzy ; gsub(" ","", xyzzy) ; print xyzzy}'
hello there my name is pax
hellotheremynameispax

Bash: How to trim whitespace before using cut

Pipe your command to awk, print the 3rd column, a space and the 4th column like this

<command> | awk '{print $3, $4}'

This results in:

12345 KB

or

<command> | awk '{print $3}'

if you want the naked number.

How to awk print a subtring and trim trailing and ending white space of the same subtring in bash

You can use sub() to substitute the white space away, and awk can do the pattern match for you, too:

xinput -list --short | awk '
    /keyboard.*slave/ { 
        s = substr($0, 7, 41);
        sub(/ *$/, "", s);
        print s;
        exit;
   }'

That would stop after the first matching line, which I suppose you wanted, since the original only acted on the first record read by awk.

So,

$ cat keyb
mouse mouse something
keyboard slave foo
keyboard slave bar
$ awk '/keyboard.*slave/ {  s = substr($0, 7, 41); sub(/ *$/, "", s); print s; exit; }'  < keyb
rd slave foo

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