How to get second last field from a cut command

问题:

I have a set of data as input and need the second last field based on deleimiter. The lines may have different numbers of delimiter. How can I get second last field ?

example input

text,blah,blaah,foo
this,is,another,text,line

expected output

blaah
text

回答1:

Got a hint from Unix cut except last two tokens and able to figure out the answer :

cat datafile | rev | cut -d '/' -f 2 | rev

回答2:

Awk is suited well for this:

awk -F, '{print $(NF-1)}' file

The variable NF is a special awk variable that contains the number of fields in the current record.

回答3:

There's no need to use cut, rev, or any other tools external to bash here at all. Just read each line into an array, and pick out the piece you want:

while IFS=, read -r -a entries; do
  printf '%s\n' "${entries[${#entries[@]} - 2]}"
done <file

Doing this in pure bash is far faster than starting up a pipeline, at least for reasonably small inputs. For large inputs, the better tool is awk.

回答4:

Code for GNU sed:

$ echo text,blah,blaah,foo|sed -r 's/^(\S+,){2}(\S+),.*/\2/'
blaah

$ echo this,is,another,text,line|sed -r 's/^(\S+,){2}(\S+),.*/\2/'
text

---

Code example similar to sudo_O's awk code:

$ sed -r 's/.*,(\w+),\w+$/\1/' file
blaah
text

It might be better to use more specialised programs for CSV files, eg. awk or excel.

回答5:

Perl solution similar to awk solution from @iiSeymour

perl -lane 'print $F[-2]' file

These command-line options are used:

• n loop around every line of the input file, do not automatically print every line

• l removes newlines before processing, and adds them back in afterwards

• a autosplit mode – split input lines into the @F array. Defaults to splitting on whitespace

• e execute the perl code

The @F autosplit array starts at index [0] while awk fields start with $1
-1 is the last element
-2 is the second to last element

回答6:

The most minimalist answer to this problem is to use my cuts utility:

$ cat file.txt
text,blah,blaah,foo
this,is,another,text,line

$ cuts -2 file.txt
blaah
text

cuts, which stands for "cut on steroids":

- automatically figures out the input field separators
- supports multi-char (and regexp) separators
- automatically pastes (side-by-side) multiple columns from multiple files
- supports negative offsets (from end of line)
- has good defaults to save typing + allows the user to override them

and much more.

I wrote cuts after being frustrated with the too many limitations of cut on Unix. It is designed to replace various cut/paste combos, slicing and dicing columns from multiple files, with multiple separator variations, while imposing minimal typing from the user.

You can get cuts (free software, Artistic Licence) from github: https://github.com/arielf/cuts/

Calling cuts without arguments will print a detailed Usage message.