How to remove leading whitespace from each line in a file

Question

I have a file that looks something like this   for  i   0  i  lt  100  i        for  i   0  i  lt  100  i      for  i   0  i  lt  100  i           for  i   0  i  lt  100  i         for  i   0  i  lt  100  i               for  i   0  i  lt  100  i    for  i   0  i  lt  100  i      I want it to look like this  remove indentations    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i      How can this be done  using sed maybe

User · Answer

Use   sed -e    s     t         name of file from which you want to remove space  gt   name  file where you want to store output    For example    sed -e  s     t       file1 txt  gt  output txt   Note   s   Substitute command   replacement for pattern      t    on each addressed line      t    Search pattern         start of the line     t   match one or more blank spaces including tab       Replace  delete  all matched patterns

User · Answer

sed  s     t      -i youfile   Warning  this will overwrite the original file

User · Answer

Here you go   user host    sed  s    t     g   lt  file-in txt   Or   user host    sed  s    t     g   lt  file-in txt  gt  file-out txt

User · Answer

For what it s worth  if you are editing this file  you can probably highlight all the lines and use your un-tab button    In Vim  use Shift   V to highlight the lines  then press  lt  lt  If you re on a Mac  then you can use Atom  Sublime Text  etc   then highlight with your mouse and then press Shift   Tab   I am not sure if there is some requirement that this must be done from the command line  If so  then  thumbs-up  to the accepted answer

User · Answer

For this specific problem  something like this would work     sed  s      g   lt  input txt  gt  output txt   It says to replace all spaces at the start of a line with nothing  If you also want to remove tabs  change it to this     sed  s     t    g   lt  input txt  gt  output txt   The leading  s  before the   means  substitute   The   s are the delimiters for the patterns  The data between the first two   s are the pattern to match  and the data between the second and third   is the data to replace it with  In this case you re replacing it with nothing  The  g  after the final slash means to do it  globally   ie  over the entire file rather than on only the first match it finds   Finally  instead of  lt  input txt  gt  output txt you can use the -i option which means to edit the file  in place   Meaning  you don t need to create a second file to contain your result  If you use this option you will lose your original file

User · Answer

You can use AWK     awk    1  1 1  file for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i      sed    sed  s     blank      g  file for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i    for  i   0  i  lt  100  i      The shell s while read loop  while read -r line do     echo  line done  lt  file

User · Answer

This Perl code edits your original file   perl -i -ne  s   s    print  file   The next one makes a backup copy before editing the original file   perl -i bak -ne  s   s    print  file   Notice that Perl borrows heavily from sed  and AWK

[unix] How to remove leading whitespace from each line in a file

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