How to insert a text at the beginning of a file

Question

So far I ve been able to find how to add a line at the beginning of a file but that s not exactly what I want  I ll show it on a example  File content  some text at the beginning   Result   lt added text gt  some text at the beginning   It s similar but I don t want to create any new line with it     I would like to do this with sed if possible

User · Answer

If the file is only one line  you can use   sed  s   insert this    oldfile  gt  newfile   If it s more than one line  one of   sed  1s   insert this    oldfile  gt  newfile sed  1 1s   insert this    oldfile  gt  newfile   I ve included the latter so that you know how to do ranges of lines  Both of these  replace  the start line marker on their affected lines with the text you want to insert  You can also  assuming your sed is modern enough  use   sed -i  whatever command you choose  filename   to do in-place editing

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Just for fun  here is a solution using ed which does not have the problem of not working on an empty file  You can put it into a shell script just like any other answer to this question    ed Test  lt  lt EOF a    0i  lt added text gt    1  1 j   g    d wq EOF   The above script adds the text to insert to the first line  and then joins the first and second line  To avoid ed exiting on error with an invalid join  it first creates a blank line at the end of the file and remove it later if it still exists   Limitations  This script does not work if  lt added text gt  is exactly equal to a single period

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Hi with carriage return   sed -i  1s   your text n   file

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There is a very easy way    echo  your header   gt  headerFile txt cat yourFile  gt  gt  headerFile txt

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my two cents   sed  -i  1i  path of file sh  filename   This will work even is the string containing forward slash

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You can use cat -  printf   s   some text at the beginning    cat - filename

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With the echo approach  if you are on macOS BSD like me  lose the -n switch that other people suggest  And I like to define a variable for the text  So it would be like this  Header  quot my complex header that may have difficult chars   quot like these quotes  quot  and line breaks  n n  quot     echo  quot  Header quot   cat  quot old txt quot      gt   quot new txt quot  mv new txt old txt

User · Answer

echo -n  text to insert    tac filename txt  tac  gt  newfilename txt   The first tac pipes the file backwards  last line first  so the  text to insert  appears last  The 2nd tac wraps it once again so the inserted line is at the beginning and the original file is in its original order

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Use subshell  echo  quot   echo -n  hello   cat filename  quot   gt  filename   Unfortunately  command substitution will remove newlines at the end of file  So as to keep them one can use  echo -n  quot hello quot    cat - filename  gt   tmp filename tmp mv  tmp filename tmp filename  Neither grouping nor command substitution is needed

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Note that on OS X  sed -i  lt pattern gt  file  fails  However  if you provide a backup extension  sed -i old  lt pattern gt  file  then file is modified in place while file old is created  You can then delete file old in your script

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Another solution with aliases  Add to your init rc  env file   addtail      find   -type f   -path     git    -exec sh -c  echo     gt  gt           addhead      find   -type f   -path     git    -exec sh -c   sed -i  1s      n              Usage   addtail  string to add at the beginning of file  addtail  string to add at the end of file

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PROBLEM  tag a file  at the top of the file  with the base name of the parent directory   I e   for   mnt Vancouver Programming file1   tag the top of file1 with Programming   SOLUTION 1 -- non-empty files   bn   PWD            bn  basename  sed -i  1s      bn   n    lt file gt    1s places the text at line 1 of the file   SOLUTION 2 -- empty or non-empty files   The sed command  above  fails on empty files   Here is a solution  based on https   superuser com questions 246837 how-do-i-add-text-to-the-beginning-of-a-file-in-bash 246841 246841  printf    PWD      n    cat -  lt file gt   gt  temp  amp  amp  mv -f temp  lt file gt    Note that the - in the cat command is required  reads standard input  see man cat for more information    Here  I believe  it s needed to take the output of the printf statement  to STDIN   and cat that and the file to temp      See also the explanation at the bottom of http   www linfo org cat html   I also added -f to the mv command  to avoid being asked for confirmations when overwriting files   To recurse over a directory   for file in    do printf    PWD      n    cat -  file  gt  temp  amp  amp  mv -f temp  file  done   Note also that this will break over paths with spaces  there are solutions  elsewhere  e g  file globbing  or find   -type f     -type solutions  for those   ADDENDUM   Re  my last comment  this script will allow you to recurse over directories with spaces in the paths      bin bash     https   stackoverflow com questions 4638874 how-to-loop-through-a-directory-recursively-to-delete-files-with-certain-extensi     To allow spaces in filenames       at the top of the script include  IFS    n   set -f      at the end of the script include  unset IFS  set  f  IFS    n   set -f    ----------------------------------------------------------------------------   SET PATHS   IN   mnt Vancouver Programming data claws-test corpus test      https   superuser com questions 716001 how-can-i-get-files-with-numeric-names-using-ls-command    FILES   find  IN -type f -regex      0-9               recursive  numeric filenames only FILES   find  IN -type f -regex      0-9                 recursive  numeric filenames only  may include spaces     echo   FILES                                           single-quoted   literally  prints   FILES    echo   FILES                                           double-quoted  prints path   filename  one per line     ----------------------------------------------------------------------------   MAIN LOOP   for f in  FILES do      Tag top of file with basename of current dir    printf   top  Tag    PWD      n n    cat -  f  gt  temp  amp  amp  mv -f temp  f      Tag bottom of file with basename of current dir    printf   n bottom  Tag    PWD      n   gt  gt   f done  unset IFS  set  f

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To add a line to the top of the file   sed -i  1iText to add

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To insert just a newline   sed  1i

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sed can operate on an address     sed -i  1s    lt added text gt     file   What is this magical 1s you see on every answer here  Line addressing    Want to add  lt added text gt  on the first 10 lines     sed -i  1 10s    lt added text gt     file   Or you can use Command Grouping       echo -n   lt added text gt     cat file     gt file new   mv file  new

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If you want to add a line at the beginning of a file  you need to add  n at the end of the string in the best solution above     The best solution will add the string  but with the string  it will not add a line at the end of a file   sed -i  1s   your text n   file

[linux] How to insert a text at the beginning of a file?

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