Save modifications in place with awk

I am learning awk and I would like to know if there is an option to write changes to file, similar to sed where I would use -i option to save modifications to a file.

I do understand that I could use redirection to write changes. However is there an option in awk to do that?

Solution 1:

In GNU Awk 4.1.0 (released 2013) and later, it has the option of "inplace" file editing:

[...] The "inplace" extension, built using the new facility, can be used to simulate the GNU "sed -i" feature. [...]

Example usage:

$ gawk -i inplace '{ gsub(/foo/, "bar") }; { print }' file1 file2 file3

To keep the backup:

$ gawk -i inplace -v INPLACE_SUFFIX=.bak '{ gsub(/foo/, "bar") }
> { print }' file1 file2 file3

Solution 2:

Unless you have GNU awk 4.1.0 or later...

You won't have such an option as sed's -i option so instead do:

$ awk '{print $0}' file > tmp && mv tmp file

Note: the -i is not magic, it is also creating a temporary file sed just handles it for you.

As of GNU awk 4.1.0...

GNU awk added this functionality in version 4.1.0 (released 10/05/2013). It is not as straight forwards as just giving the -i option as described in the released notes:

The new -i option (from xgawk) is used for loading awk library files. This differs from -f in that the first non-option argument is treated as a script.

You need to use the bundled inplace.awk include file to invoke the extension properly like so:

$ cat file
123 abc
456 def
789 hij

$ gawk -i inplace '{print $1}' file

$ cat file
123
456
789

The variable INPLACE_SUFFIX can be used to specify the extension for a backup file:

$ gawk -i inplace -v INPLACE_SUFFIX=.bak '{print $1}' file

$ cat file
123
456
789

$ cat file.bak
123 abc
456 def
789 hij

I am happy this feature has been added but to me, the implementation isn't very awkish as the power comes from the conciseness of the language and -i inplace is 8 characters too long i.m.o.

Here is a link to the manual for the official word.