sed edit file in place

Question

I am trying to find out if it is possible to edit a file in a single sed command without manually streaming the edited content into a new file and

Answer 1

If you are replacing the same amount of characters and after carefully reading “In-place” editing of files...

You can also use the redirection operator <> to open the file to read and write:

sed 's/foo/bar/g' file 1<> file

See it live:

$ cat file
hello
i am here                           # see "here"
$ sed 's/here/away/' file 1<> file  # Run the `sed` command
$ cat file
hello
i am away                           # this line is changed now

From Bash Reference Manual → 3.6.10 Opening File Descriptors for Reading and Writing:

The redirection operator

[n]<>word

causes the file whose name is the expansion of word to be opened for both reading and writing on file descriptor n, or on file descriptor 0 if n is not specified. If the file does not exist, it is created.

Answer 2

mv file.txt file.tmp && sed 's/foo/bar/g' < file.tmp > file.txt

Should preserve all hardlinks, since output is directed back to overwrite the contents of the original file, and avoids any need for a special version of sed.

Answer 3

You could use vi

vi -c '%s/foo/bar/g' my.txt -c 'wq'

Answer 4

You didn't specify what shell you are using, but with zsh you could use the =( ) construct to achieve this. Something along the lines of:

cp =(sed ... file; sync) file

=( ) is similar to >( ) but creates a temporary file which is automatically deleted when cp terminates.

Answer 5

sed supports in-place editing. From man sed:

-i[SUFFIX], --in-place[=SUFFIX]

    edit files in place (makes backup if extension supplied)

Example:

Let's say you have a file hello.txtwith the text:

hello world!

If you want to keep a backup of the old file, use:

sed -i.bak 's/hello/bonjour' hello.txt

You will end up with two files: hello.txt with the content:

bonjour world!

and hello.txt.bak with the old content.

If you don't want to keep a copy, just don't pass the extension parameter.

Answer 6

Note that on OS X you might get strange errors like "invalid command code" or other strange errors when running this command. To fix this issue try

sed -i '' -e "s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g" <file>

This is because on the OSX version of sed, the -i option expects an extension argument so your command is actually parsed as the extension argument and the file path is interpreted as the command code. Source: https://stackoverflow.com/a/19457213