Prepend a text to a file.

sed -i '1s/^/text to prepend\n/' file1
Using the sed -i (inline), you can replace the beginning of the first line of a file without redirecting the output to a temporary location.

4
By: xeor
2011-06-25 12:02:11

4 Alternatives + Submit Alt

What Others Think

Sed has the -i switch for "in-place" editing. First of all, only some implementations of sed (GNU sed and BSD sed AFAIK) support -i. It's a nonstandard extension, and as such not universally available. According to the documentation (at least GNU sed's), what sed does when -i is specified is create a temporary file, send output to that file, and at the end, that file is renamed to the original name. This can be verified with strace; even without strace, a simple "ls -i" of the file before and after sed operates will show two different inode numbers.
RanyAlbeg · 534 weeks and 6 days ago
But at least it does it for us.
kaedenn · 534 weeks and 6 days ago
In a nonstandard way. And it makes sense, since sed is a STREAM editor so the "in-place" option *should* be a nonstandard one by that logic.
RanyAlbeg · 534 weeks and 6 days ago
A good use of this would be: sed -i '1s/^/#!\/usr\/bin\/env python\n\n/' myscript.py
ewilson · 534 weeks and 4 days ago
echo "text to prepend $(cat output.log)" > output.log
lapinpt · 343 weeks and 5 days ago
echo "text to prepend" | cat - output.log | sponge output.log
lapinpt · 343 weeks and 5 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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