Adds guide page for bash command grep (#25769)

guide/english/bash/bash-grep/index.md

@@ -1,29 +1,46 @@
 ---
-title: Bash Grep
+title: Bash grep
 ---
- ## Bash command: grep
+## Bash command: grep
- `grep` stands for Global Regular Expression Print. It is used to search piped input or files for a string which can contain regex.
+
- 
+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.
- ### Usage
+
- ```
+### Usage
- grep <some string> <file name>
+
- ```
+```bash
- 
+grep [options] [pattern] [file_names]
- Commonly used options:
+```
- * `-i` - Ignores the case when performing the search.
+Common options:
- * `-v` - Inverts the search and only selects lines that do not match the search string.
+
- 
+* `-i`, Ignore case when mathing the provided pattern
- ### Examples
+* `-v`, Show results which do not match the provided pattern.
- #### Search for IP 127.0.0.1 in the /etc/hosts file
+* `-l`, Instead of outputting matching lines, output the file paths which contain matching text.
+* `-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)
+* `-c`, Output a count of the matching lines.
+* `-E`, Use extended regular expressions to define the pattern to be matched. The command alias `egrep` is the same as `grep -E`
+
+### Examples:
+
+Search a server log file for lines containing the text "ERROR":
+```bash
+grep ERROR server.log
+```
+
+Using a pipe to combine commands, list files and folders in the current working directory that contain the text "code":
+```bash
+ls | grep code
+```
+
+Search for IP 127.0.0.1 in the /etc/hosts file
  ```bash
  grep "127.0.0.1" /etc/hosts
  ```
  
- #### Search for oom (out of memory) in /var/log/messages
+Search for oom (out of memory) in /var/log/messages
  ```bash
  grep -i oom /var/log/messages
  ```
  
  ### More Information
- * run `man grep` for a full list of available flags/options to use.
+* [Bash Guide for Beginners, Examples using grep](https://tldp.org/LDP/Bash-Beginners-Guide/html/sect_04_02.html)
- * [Wikipedia](https://en.wikipedia.org/wiki/Grep)
+* [Wikipedia](https://en.wikipedia.org/wiki/Grep)