47 lines
1.6 KiB
Markdown
47 lines
1.6 KiB
Markdown
---
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title: Bash grep
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---
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## Bash command: grep
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The `grep` command is used to find matching text in input file(s). Default output lists lines from the input file(s) which contain a match to the provided pattern. Options may be used to alter matching behavior or to provide a different output scheme.
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### Usage
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```bash
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grep [options] [pattern] [file_names]
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```
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Common options:
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* `-i`, Ignore case when mathing the provided pattern
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* `-v`, Show results which do not match the provided pattern.
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* `-l`, Instead of outputting matching lines, output the file paths which contain matching text.
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* `-r`, Search all files in the provided directories. Directory name(s) or path(s) is used in place of the file name(s) (Search defaults to the current working directory if none is provided)
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* `-c`, Output a count of the matching lines.
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* `-E`, Use extended regular expressions to define the pattern to be matched. The command alias `egrep` is the same as `grep -E`
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### Examples:
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Search a server log file for lines containing the text "ERROR":
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```bash
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grep ERROR server.log
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```
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Using a pipe to combine commands, list files and folders in the current working directory that contain the text "code":
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```bash
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ls | grep code
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```
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Search for IP 127.0.0.1 in the /etc/hosts file
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```bash
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grep "127.0.0.1" /etc/hosts
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```
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Search for oom (out of memory) in /var/log/messages
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```bash
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grep -i oom /var/log/messages
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```
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### More Information
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* [Bash Guide for Beginners, Examples using grep](https://tldp.org/LDP/Bash-Beginners-Guide/html/sect_04_02.html)
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* [Wikipedia](https://en.wikipedia.org/wiki/Grep)
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