How can I extract the last field in a string?

Question

How can I extract the last field in a string? I have a string:

xres = 0: +*VGA1 1600/423x900/238+0+0  VGA1

I want to extract the last part of the string, that is VGA1.

Answer 1

You can use rev and cut if the string has delimiters, as in your case:

var="xres = 0: +*VGA1 1600/423x900/238+0+0  VGA1"
rev <<< "$var" | cut -f1 -d' ' | rev
# output => VGA1

• the first rev reverses the string so that the last token shifts to the beginning, though in reverse
• cut -f1 extracts the first field, using space as the delimiter
• the second rev reverses the extracted field to its original state

The good thing about this solution is that it doesn't depend upon how many fields precede the last token.

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Related post: How to find the last field using 'cut'

Answer 2

If this string always contains the same number of spaces, we can consider each space-separated part as a field and use cut to extract it :

$ echo "xres = 0: +*VGA1 1600/423x900/238+0+0  VGA1" | cut -d' ' -f7
VGA1

If that's not the case, we can use regex to match from the end, for example with grep :

$ echo "xres = 0: +*VGA1 1600/423x900/238+0+0  VGA1" | grep -o '[^ ]*$'
VGA1

Answer 3

One way to do it with Bash builtins only (no external commands) :

var="xres = 0: +*VGA1 1600/423x900/238+0+0  VGA1"
[[ "$var" =~ [[:space:]]([^[:space:]]+)([[:space:]]*)$ ]]
match="${BASH_REMATCH[1]-}"

Please note the regular expression used will tolerate trailing whitespace in the string ; it could be simplified to avoid that if it is considered a bug rather than a feature :

[[ "$var" =~ [[:space:]]([^[:space:]]+)$ ]]

Answer 4

I took a different approach:

echo "xres = 0: +*VGA1 1600/423x900/238+0+0  VGA1" | \
sed 's/ /\
/g' | tail -n1

Answer 5

I would use awk:

$ awk '{print $NF}' <<< 'xres = 0: +*VGA1 1600/423x900/238+0+0  VGA1'
VGA1

NF is the number of fields in the record, and $NF prints the field with number NF, i.e., the last one. Fields are by default blank separated.

Alternatively, using shell parameter expansion:

$ str='xres = 0: +*VGA1 1600/423x900/238+0+0  VGA1'
$ echo "${str##* }"
VGA1

This removes the longest matching string from the beginning, where the pattern to match is * : "anything, followed by a space".