TIL

Bash pattern substitution

Context

I wanted a script to make it quick to generate consistent templates for this repo, so I wanted to take the subject (in this case Bash pattern substitution), and replace the spaces with underscores.

TIL

We can replace underscores in a string with straight up Bash parameter substitution.

variable=${variable// /_}

• variable is the variable name, I think that’s obvious.
• // is the command to replace every occurance of the pattern in the string (a single slash [/] will just do the first occurance)
• ` ` is the pattern to look for… I’m looking for spaces.
• _ is the pattern to replace it with… I’m replacing it with underscores. Omitting the replacement would just delete the pattern from the string.

A generalized form of this would be:

variable=${variable//*PATTERN*/*REPLACEMENT*}

Sources and References

• Stack Overflow - Replace spaces with underscores via BASH
• The Linux Documentatiuon Project - Parameter Substitution - Variable Expansion / Substring replacement

Date

Wednesday, February 19th, 2025
2025-02-19

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