57 lines
1.7 KiB
Markdown
57 lines
1.7 KiB
Markdown
---
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tags:
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- shell
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---
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# Grep
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## Purpose of `grep`
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`grep` stands for “global regular expression print”. It allows you to search
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plain text data sets for strings which match a regular expression or pattern.
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## Syntax
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### Schematic
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```bash
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grep [options] [pattern] [source file] > [output file]
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```
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Note that above we redirect the file matches to a new file. You don't have to do
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this. If you omit the redirection, `grep` will output to standard output.
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### Applied
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```bash
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grep -i -n "banana" fruits.txt > banana.txt
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```
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The above example searches, using regex, for strings matching the pattern
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“banana” in the file `fruits.txt` regardless of the character case (`-i` ensures
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this) and outputs its findings to the file `banana.txt`, with the line number
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where the match occurs appended to the output (`-n` takes care of this).
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Note that for simplicity, you can chain optional values together, i.e. the
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options in the above example could be input as `-in`.
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## Useful options
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- ignore case: `i`
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- count matches instead of returning actual match: `-c`
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- precede each match with the line number where it occurs: `-n`
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- invert the match (show everything that doesn't match the expression): `-v`
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- search entire directories recursively: `-r`
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- list file names where matches occur (in the scenario of a recursive match):
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`-l`
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## `ripgrep`
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`ripgrep` is generally faster however it does not come as default with Unix and
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only works recursively, i.e. it is designed to find strings within files within
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multiple directories not just single files or piped streams.
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It also respects `.gitignore` files that it finds within directories by default
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and `node_modules` which is really handy.
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Most of the standard `grep` options transfer over.
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