How can I add a string to the beginning of each file in a folder in bash?

Question

I want to be able to prepend a string to the beginning of each text file in a folder. How can I do this using bash on Linux?

score 31 · Accepted Answer · answered Apr 26 '11 at 21:31

31

This will do that. You could make it more efficient if you are doing the same text to each file...

for f in *; do 
  echo "whatever" > tmpfile
  cat $f >> tmpfile
  mv tmpfile $f
done

answered Apr 26 '11 at 21:31

drysdam

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9

Both `$f` should be `"$f"`. It would be good to do some error checking too. Also, it changes permissions and ownership of the original file. – ikegami Apr 26 '11 at 21:38

score 25 · Answer 2 · answered Apr 27 '11 at 00:06

25

You can do it like this without a loop and cat

sed -i '1i whatever' *

if you want to back up your files, use -i.bak

Or using awk

awk 'FNR==1{$0="whatever\n"$0;}{print $0>FILENAME}' *

answered Apr 27 '11 at 00:06

ghostdog74

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your sed comman seems to prepend the string only to the first file – Raffael Dec 18 '14 at 17:15
Why this answer is in the bottom?! – Manuel Spigolon Aug 13 '21 at 11:53

score 5 · Answer 3 · answered Apr 26 '11 at 22:37

5

And you can do this using sed in 1 single command as well

for f in *; do
  sed -i.bak '1i\
  foo-bar
  ' ${f}
done

answered Apr 26 '11 at 22:37

anubhava

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score 0 · Answer 4 · edited Jan 04 '13 at 21:42

0

This is the easiest I have worked out.

sed -i '1s/^/Text to add then new file\n/' /file/to/change

edited Jan 04 '13 at 21:42

Taryn

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answered Jan 04 '13 at 21:19

Jay Stan

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score 0 · Answer 5 · edited Aug 25 '19 at 12:44

0

Here is an example :

for f in *; 
do
    mv "$f" "whatever_$f"
done

edited Aug 25 '19 at 12:44

Mohammad Reza Shahrestani

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answered Aug 24 '19 at 07:14

IK Cheng

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I wanted to format but did not know how to as I'm new here. – IK Cheng Aug 25 '19 at 10:28
Go start from here : https://stackoverflow.com/help/formatting and while you are typing an answer or question see rightbar there is help for formatting – Mohammad Reza Shahrestani Aug 25 '19 at 10:34

score 0 · Answer 6 · answered Apr 26 '11 at 21:32

0

This should do the trick.

FOLDER='path/to/your/folder'
TEXT='Text to prepend'
cd $FOLDER
for i in `ls -1 $FOLDER`; do
     CONTENTS=`cat $i`
     echo $TEXT > $i  # use echo -n if you want the append to be on the same line
     echo $CONTENTS >> $i
done

I wouldn't recommending doing this if your files are very big though.

answered Apr 26 '11 at 21:32

Cfreak

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this is a useless use of `ls` example. Use shell expansion. – ghostdog74 Apr 27 '11 at 00:04

score 0 · Answer 7 · answered Apr 26 '11 at 22:25

You can do this as well:

for f in *; do
  cat <(echo "someline") $f > tempfile
  mv tempfile $f
done

It's not much different from the 1st post but does show how to treat the output of the 'echo' statement as a file without having to create a temporay file to store the value.

score 0 · Answer 8 · answered Apr 27 '11 at 13:54

You may use the ed command to do without temporary files if you like:

for file in *; do
  (test ! -f "${file}" || test ! -w "${file}") && continue                # sort out non-files and non-writable files
  if test -s "${file}" && ! grep -Iqs '.*' "${file}"; then continue; fi   # sort out binary files
  printf '\n%s\n\n' "FILE:  ${file}"
  # cf. http://wiki.bash-hackers.org/howto/edit-ed
  printf '%s\n' H 0a "foobar" . ',p' q | ed -s "${file}"  # dry run (just prints to stdout)
  #printf '%s\n' H 0a "foobar" . wq | ed -s "${file}"     # in-place file edit without any backup
done | less

score -1 · Answer 9 · answered May 15 '19 at 02:45

-1

A one-liner: rename '' string_ *

answered May 15 '19 at 02:45

user151841

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How can I add a string to the beginning of each file in a folder in bash?

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