CLI – sed

Screen Shot 2018-08-06 at 7.16.16 PM.png

CLI – Sometimes you have a file that you wish to scan for every instance of a phrase and replace it with another phrase. The sed or stream editor command is just what you are looking for. In the above screen shot I first display a file with the cat command, then use se to replace all appearances of the word ‘Emma’ with the word ‘Bambi’. The sed command syntax for that is:

sed  ‘s/Emma/Bambi/g’ Review_Four\ Dominions\ copy.txt

The ‘s/Emma/Bambi/g’ says to do a global search and replace of Bambi for every instance of Emma. The name of the file being operated on is ‘Review_Four\ Dominions\ copy.txt’.

The description of sed in the macOS man page is:

The sed utility reads the specified files, or the standard input if no files are specified, modifying the input as specified by a list of commands.  The input is then written to the standard output.

A single command may be specified as the first argument to sed.  Multiple commands may be specified by using the -e or -f options.  All commands are applied to the input in the order they are specified regardless of  their origin.

This can be a very powerful and useful command when processing text files. In the SysAdmin world it can be very useful for updating configuration files.

To learn a lot more about how to use sed, take a look at “‘Sed’ Command In Linux: Useful Applications Explained“. Yes, this is a Linux article, but the sed command as implemented on macOS is fundamentally the same.

See my other CLI and macOS articles


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