Operation and Maintenance
Linux Operation and Maintenance
How to find and replace text in a file from the Linux terminal
How to find and replace text in a file from the Linux terminal
To replace text in a file from the Linux terminal, use sed for simple substitutions and perl for advanced regex; sed -i 's/old/new/g' filename replaces all occurrences in place, with -i.bak creating a backup, and alternative delimiters like | handle slashes; add i flag for case-insensitive matching, while perl -i -pe enables complex patterns with word boundaries or lookaheads, ideal for precise replacements across single or multiple files when combined with find or grep.
To find and replace text in a file from the Linux terminal, the most common and powerful tool is sed (stream editor). You can also use perl or awk for more complex cases. Below are practical methods using these tools directly in the terminal.
Using sed for find and replace
sed is ideal for simple text substitutions in files. By default, it outputs changes to stdout, so you need to use the -i flag to edit the file in place.
- To replace the first occurrence of "old-text" with "new-text" in each line:
- To replace all occurrences in each line, add the g (global) flag:
- If you want to create a backup before editing, use -i.bak:
Handling special characters
If your text contains forward slashes (/), you can change the delimiter in sed to another character like | or #.
- Example: Replace /path/to/old with /path/to/new
Case-insensitive replacement
Add the i flag to perform case-insensitive matching.
sed -i 's/old-text/new-text/gi' filenameThis replaces "Old-Text", "OLD-TEXT", etc., as well.
Using perl for advanced replacements
perl offers more flexibility, especially with regular expressions.
- Basic in-place replacement:
- With backup:
Perl supports advanced patterns, such as word boundaries (\b) or lookaheads, which can be useful for precise matches.
These methods work well for single files. For multiple files, combine them with find or grep. Just be careful — always test without -i first to preview changes. Basically, stick to sed for most tasks, and use perl when you need regex power.
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