Diff for "BashFAQ/090"

Differences between revisions 3 and 5 (spanning 2 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:

ed -s file << EOF
1i
header line 1
header line 2
.
w
EOF

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 you can rewrite the file, using things like:

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

or lots of other solutions.

-  ⇤ ← Revision 3 as of 2008-11-22 14:09:11 → 
  Size: 449
  Editor: localhost
  Comment: converted to 1.6 markup
+   ← Revision 5 as of 2009-01-09 14:09:01 → ⇥
  Size: 651
  Editor: 212
  Comment:
-Deletions are marked like this.
+Additions are marked like this.
 Line 3:
+You cannot do it with bash redirections alone; the opposite of `>>` does not exist....
-Line 4:
+Line 5:
-You cannot do it with bash redirections only, ie the opposite of >> does not exist.

You can use an editor:
+To insert content at the beginning of a file, you can use an editor:
-Line 16:
+Line 15:
-you can use things like:
+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 you can rewrite the file, using things like:
-Line 22:
+Line 23:
-or a gazillion of other solutions
+or lots of other solutions.