How to find the last field using 'cut'

Question

Without using sed or awk, only cut, how do I get the last field when the number of fields are unknown or change with every line?

Answer 1

You could try something like this:

echo 'maps.google.com' | rev | cut -d'.' -f 1 | rev

Explanation

• maps.google.com's reverse will be moc.elgoog.spam
• cut uses dot as the delimiter and chooses the first field, which is moc
• lastly, we reverse it again (thanks for the reminder, @tom) to get com

Answer 2

Use a parameter expansion. This is much more efficient than any kind of external command, cut (or grep) included.

data=foo,bar,baz,qux
last=${data##*,}

See BashFAQ #100 for an introduction to native string manipulation in bash.

Answer 3

It is not possible using just cut. Here is a way using grep:

grep -o '[^,]*$'

Replace the comma for other delimiters.

Answer 4

Without awk ?... But it's so simple with awk:

echo 'maps.google.com' | awk -F. '{print $NF}'

AWK is a way more powerful tool to have in your pocket. -F if for field separator NF is the number of fields (also stands for the index of the last)

Answer 5

There are multiple ways. You may use this too.

echo "Your string here"| tr ' ' '\n' | tail -n1
> here

Obviously, the blank space input for tr command should be replaced with the delimiter you need.

Answer 6

This is the only solution possible for using nothing but cut:

echo "s.t.r.i.n.g." | cut -d'.' -f2- [repeat_following_part_forever_or_until_out_of_memory:] | cut -d'.' -f2-

Using this solution, the number of fields can indeed be unknown and vary from time to time. However as line length must not exceed LINE_MAX characters or fields, including the new-line character, then an arbitrary number of fields can never be part as a real condition of this solution.

Yes, a very silly solution but the only one that meets the criterias I think.

Answer 7

the following implements A friend's suggestion

#!/bin/bash
rcut(){

  nu="$( echo $1 | cut -d"$DELIM" -f 2-  )"
  if [ "$nu" != "$1" ]
  then
    rcut "$nu"
  else
    echo "$nu"
  fi
}

$ export DELIM=.
$ rcut a.b.c.d
d

Answer 8

If you have a file named filelist.txt that is a list paths such as the following: c:/dir1/dir2/file1.h c:/dir1/dir2/dir3/file2.h

then you can do this: rev filelist.txt | cut -d"/" -f1 | rev

Answer 9

If your input string doesn't contain forward slashes then you can use basename and a subshell:

$ basename "$(echo 'maps.google.com' | tr '.' '/')"

This doesn't use sed or awk but it also doesn't use cut either, so I'm not quite sure if it qualifies as an answer to the question as its worded.

This doesn't work well if processing input strings that can contain forward slashes. A workaround for that situation would be to replace forward slash with some other character that you know isn't part of a valid input string. For example, the pipe (|) character is also not allowed in filenames, so this would work:

$ basename "$(echo 'maps.google.com/some/url/things' | tr '/' '|' | tr '.' '/')" | tr '|' '/'

Answer 10

Adding an approach to this old question just for the fun of it:

$ cat input.file # file containing input that needs to be processed
a;b;c;d;e
1;2;3;4;5
no delimiter here
124;adsf;15454
foo;bar;is;null;info

$ cat tmp.sh # showing off the script to do the job
#!/bin/bash
delim=';'
while read -r line; do  
    while [[ "$line" =~ "$delim" ]]; do
        line=$(cut -d"$delim" -f 2- <<<"$line")
    done
    echo "$line"
done < input.file

$ ./tmp.sh # output of above script/processed input file
e
5
no delimiter here
15454
info

Besides bash, only cut is used. Well, and echo, I guess.

Answer 11

I realized if we just ensure a trailing delimiter exists, it works. So in my case I have comma and whitespace delimiters. I add a space at the end;

$ ans="a, b"
$ ans+=" "; echo ${ans} | tr ',' ' ' | tr -s ' ' | cut -d' ' -f2
b