Rearrange columns using cut

问题:

I am having a file in the following format

Column1    Column2
str1       1
str2       2
str3       3

I want the columns to be rearranged. I tried below command

cut -f2,1 file.txt

The command doesn't reorder the columns. Any idea why its not working?

Thank you.

回答1:

For the cut(1) man page:

Use one, and only one of -b, -c or -f. Each LIST is made up of one range, or many ranges separated by commas. Selected input is written in the same order that it is read, and is written exactly once.

It reaches field 1 first, so that is printed, followed by field 2.

Use awk instead:

awk '{ print $2 " " $1}' file.txt

回答2:

You may also combine cut and paste:

paste <(cut -f2 file.txt) <(cut -f1 file.txt)

via comments: It's possible to avoid bashisms and remove one instance of cut by doing:

paste file.txt file.txt | cut -f2,3

回答3:

using just the shell,

while read -r col1 col2
do
  echo $col2 $col1
done <"file"

回答4:

You can use Perl for that:

perl -ane 'print "$F[1] $F[0]\n"' < file.txt

• -e option means execute the command after it
• -n means read line by line (open the file, in this case STDOUT, and loop over lines)
• -a means split such lines to a vector called @F ("F" - like Field). Perl indexes vectors starting from 0 unlike cut which indexes fields starting form 1.
• You can add -F pattern (with no space between -F and pattern) to use pattern as a field separator when reading the file instead of the default whitespace

The advantage of running perl is that (if you know Perl) you can do much more computation on F than rearranging columns.

回答5:

Just been working on something very similar, I am not an expert but I thought I would share the commands I have used. I had a multi column csv which I only required 4 columns out of and then I needed to reorder them.

My file was pipe '|' delimited but that can be swapped out.

LC_ALL=C cut -d$'|' -f1,2,3,8,10 ./file/location.txt | sed -E "s/(.*)\|(.*)\|(.*)\|(.*)\|(.*)/\3\|\5\|\1\|\2\|\4/" > ./newcsv.csv

Admittedly it is really rough and ready but it can be tweaked to suit!

回答6:

Using join:

join -t $'\t' -o 1.2,1.1 file.txt file.txt

---

Notes:

• -t $'\t' In GNU join the more intuitive -t '\t' without the $ fails, (coreutils v8.28 and earlier?); it's probably a bug that a workaround like $ should be necessary. See: unix join separator char.

• join needs two filenames, even though there's just one file being worked on. Using the same name twice tricks join into performing the desired action.

• For systems with low resources join offers a smaller footprint than some of the tools used in other answers:

  wc -c $(realpath `which cut join sed awk perl`) | head -n -1
    43224 /usr/bin/cut
    47320 /usr/bin/join
   109840 /bin/sed
   658072 /usr/bin/gawk
  2093624 /usr/bin/perl