Diff for "BashFAQ/090"

Differences between revisions 5 and 9 (spanning 4 versions)

How do I prepend a text to a file (the opposite of >>)?

You cannot do it with bash redirections alone; the opposite of >> does not exist....

To insert content at the beginning of a file, you can use an editor, for example ex:

ex file << EOF
0a
header line 1
header line 2
.
w
EOF

or ed:

printf '%s\n' 0a "line 1" "line 2" . w | ed -s file

ex will also add a newline character to the end of the file if it's missing.

Or you can rewrite the file, using things like:

{ echo line; cat file ;} >tmpfile && mv tmpfile file
echo line | cat - file > tmpfile && mv tmpfile file

Some people insist on using the sed hammer to pound in all the screws:

sed "1iTEXTTOPREPEND" filename > tmp &&
mv tmp filename

There are lots of other solutions as well.

-  ⇤ ← Revision 5 as of 2009-01-09 14:09:01 → 
  Size: 651
  Editor: 212
  Comment:
+   ← Revision 9 as of 2011-03-15 17:02:32 → ⇥
  Size: 903
  Editor: GreyCat
  Comment: ed
-Deletions are marked like this.
+Additions are marked like this.
 Line 5:
-To insert content at the beginning of a file, you can use an editor:
+To insert content at the beginning of a file, you can use an editor, for example `ex`:
 Line 7:
-ed -s file << EOF
1i
+ex file << EOF
0a
 Line 15:
-Please note that this will not work if the file is empty. ed will also add a newline character to the end of the file if it's missing.
+or [[http://bash-hackers.org/wiki/doku.php?id=howto:edit-ed|ed]]:
{{{
printf '%s\n' 0a "line 1" "line 2" . w | ed -s file
}}}

`ex` will also add a newline character to the end of the file if it's missing.
-Line 23:
+Line 29:
-or lots of other solutions.
+Some people insist on using the `sed` hammer to pound in all the screws:
{{{
sed "1iTEXTTOPREPEND" filename > tmp &&
mv tmp filename
}}}

There are lots of other solutions as well.