Rearrange columns using cut

Question

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

User · Answer

Expanding on the answer from  Met  also using Perl  If the input and output are TAB-delimited  perl -F  t  -lane  print join  quot  t quot    F 1  0   in file  If the input and output are whitespace-delimited  perl -lane  print join  quot   quot    F 1  0   in file  Here  -e tells Perl to look for the code inline  rather than in a separate script file  -n reads the input 1 line at a time  -l removes the input record separator   n on  NIX  after reading the line  similar to chomp   and add output record separator   n on  NIX  to each print  -a splits the input line on whitespace into array  F  -F  t  in combination with -a splits the input line on TABs  instead of whitespace into array  F   F 1  0  is the array made up of the 2nd and 1st elements of array  F  in this order  Remember that arrays in Perl are zero-indexed  while fields in cut are 1-indexed  So fields in  F 0  1  are the same fields as the ones in cut -f1 2  Note that such notation enables more flexible manipulation of input than in some other answers posted above  which are fine for a simple task   For example    reverses the order of fields  perl -F  t  -lane  print join  quot  t quot   reverse  F  in file    prints last and first fields only  perl -F  t  -lane  print join  quot  t quot    F -1  0   in file

User · Answer

You can use Perl for that   perl -ane  print   F 1   F 0  n    lt  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

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Using sed  Use sed with basic regular expression s nested subexpressions to capture and reorder the column content   This approach is best suited when there are a limited number of cuts to reorder columns  as in this case   The basic idea is to surround interesting portions of the search pattern with    and     which can be played back in the replacement pattern with    where   represents the sequential position of the subexpression in the search pattern   For example     echo  foo bar    sed  s   foo     bar    2  1     yields   bar foo   Text outside a subexpression is scanned but not retained for playback in the replacement string   Although the question did not discuss fixed width columns  we will discuss here as this is a worthy measure of any solution posed   For simplicity let s assume the file is space delimited although the solution can be extended for other delimiters   Collapsing Spaces  To illustrate the simplest usage  let s assume that multiple spaces can be collapsed into single spaces  and the the second column values are terminated with EOL  and not space padded    File   bash-3 2  cat f Column1    Column2 str1       1 str2       2 str3       3 bash-3 2  od -a f 0000000    C   o   l   u   m   n   1  sp  sp  sp  sp   C   o   l   u   m 0000020    n   2  nl   s   t   r   1  sp  sp  sp  sp  sp  sp  sp   1  nl 0000040    s   t   r   2  sp  sp  sp  sp  sp  sp  sp   2  nl   s   t   r 0000060    3  sp  sp  sp  sp  sp  sp  sp   3  nl  0000072   Transform   bash-3 2  sed  s                             2  1   f Column2 Column1 1 str1 2 str2 3 str3 bash-3 2  sed  s                             2  1   f   od -a 0000000    C   o   l   u   m   n   2  sp   C   o   l   u   m   n   1  nl 0000020    1  sp   s   t   r   1  nl   2  sp   s   t   r   2  nl   3  sp 0000040    s   t   r   3  nl 0000045   Preserving Column Widths  Let s now extend the method to a file with constant width columns  while allowing columns to be of differing widths   File   bash-3 2  cat f2 Column1    Column2 str1       1 str2       2 str3       3 bash-3 2  od -a f2 0000000    C   o   l   u   m   n   1  sp  sp  sp  sp   C   o   l   u   m 0000020    n   2  nl   s   t   r   1  sp  sp  sp  sp  sp  sp  sp   1  sp 0000040   sp  sp  sp  sp  sp  nl   s   t   r   2  sp  sp  sp  sp  sp  sp 0000060   sp   2  sp  sp  sp  sp  sp  sp  nl   s   t   r   3  sp  sp  sp 0000100   sp  sp  sp  sp   3  sp  sp  sp  sp  sp  sp  nl 0000114   Transform   bash-3 2  sed  s                                      3 4  1 2   f2 Column2 Column1 1       str1       2       str2       3       str3       bash-3 2  sed  s                                      3 4  1 2   f2   od -a 0000000    C   o   l   u   m   n   2  sp   C   o   l   u   m   n   1  sp 0000020   sp  sp  nl   1  sp  sp  sp  sp  sp  sp  sp   s   t   r   1  sp 0000040   sp  sp  sp  sp  sp  nl   2  sp  sp  sp  sp  sp  sp  sp   s   t 0000060    r   2  sp  sp  sp  sp  sp  sp  nl   3  sp  sp  sp  sp  sp  sp 0000100   sp   s   t   r   3  sp  sp  sp  sp  sp  sp  nl  0000114   Lastly although the question s example does not have strings of unequal length  this sed expression support this case   File   bash-3 2  cat f3 Column1    Column2 str1       1       string2    2       str3       3         Transform   bash-3 2  sed  s                                      3 4  1 2   f3 Column2 Column1    1       str1       2       string2    3       str3     bash-3 2  sed  s                                      3 4  1 2   f3   od -a 0000000    C   o   l   u   m   n   2  sp   C   o   l   u   m   n   1  sp 0000020   sp  sp  nl   1  sp  sp  sp  sp  sp  sp  sp   s   t   r   1  sp 0000040   sp  sp  sp  sp  sp  nl   2  sp  sp  sp  sp  sp  sp  sp   s   t 0000060    r   i   n   g   2  sp  sp  sp  nl   3  sp  sp  sp  sp  sp  sp 0000100   sp   s   t   r   3  sp  sp  sp  sp  sp  sp  nl  0000114   Comparison to other methods of column reordering under shell   Surprisingly for a file manipulation tool  awk is not well-suited for cutting from a field to end of record   In sed this can be accomplished using regular expressions  e g    xxx      where xxx is the expression to match the column  Using paste and cut subshells gets tricky when implementing inside shell scripts   Code that works from the commandline fails to parse when brought inside a shell script   At least this was my experience  which drove me to this approach

User · Answer

using just the shell    while read -r col1 col2 do   echo  col2  col1 done  lt  file

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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

User · Answer

Just as an addition to answers that suggest to duplicate the columns and then to do cut  For duplication  paste etc  will work only for files  but not for streams  In that case  use sed instead  cat file txt   sed s        amp  t amp      cut -f2 3 This works on both files and streams  and this is interesting if instead of just reading from a file with cat  you do something interesting before re-arranging the columns  By comparison  the following does not work  cat file txt   paste - -   cut -f2 3 Here  the double stdin placeholder paste does not duplicate stdin  but reads the next line

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You may also combine cut and paste   paste  lt  cut -f2 file txt   lt  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

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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    gt    newcsv csv   Admittedly it is really rough and ready but it can be tweaked to suit

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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

[shell] Rearrange columns using cut

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