Improve Command Line Productivity - RHCSA (RH134).pdf
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The document provides an overview of using command line utilities and shell scripts, including how to interact with various shells in Linux, create and execute shell scripts, and utilize the 'grep' command for searching text patterns. It includes commands for accessing shell information, managing script permissions, and executing loops and conditionals within scripts. Additionally, it outlines options for the 'grep' command and introduces 'egrep' for complex pattern matching.
![If-Then & loop scripts
● If-Then: Conditional execution of code.
● Syntax:
`if [ condition ]; then action; fi`
● loop: Repeated execution of code.
● Syntax for 'for' loop:
`for i in {start..end}; do action; done`](https://image.slidesharecdn.com/improvecommandlineproductivity-rhcsarh134-241007071550-c999075c/85/Improve-Command-Line-Productivity-RHCSA-RH134-pdf-9-320.jpg)
![grep
● Command-line utility used for searching text patterns within
files
● Syntax:
● [options]: Optional flags that modify the behavior of grep.
● pattern: The text pattern to search for.
● [file...]: files to search within
● To search for more than one keyword use :
egrep –i “keyword|keyword2” file](https://image.slidesharecdn.com/improvecommandlineproductivity-rhcsarh134-241007071550-c999075c/85/Improve-Command-Line-Productivity-RHCSA-RH134-pdf-16-320.jpg)
Improve Command Line Productivity - RHCSA (RH134).pdf
- 1. Improve Command line utility: Shell Scripts
- 2. Shell ● CLI which allows user to interact with OS ● For example :- ○ In linux sh, bash etc. is a shell ● Use echo $0 to get your shell name ● Available shells are stored in /etc/shells
- 4. For knowing the current shell name ● Command: echo $0 To know the specific version of the shell being used ● Command: echo $BASH_VERSION
- 5. List all the available shells on the system ● Command: cat /etc/shells
- 6. Verify which shell is assigned to a user ● Command: cat /etc/passwd
- 7. Shell Scripts Executable file comprising a series of shell commands executed in sequence. Within the file, you can include: ● Shell declaration (#!/bin/bash) ● Commentary lines (# comments) ● Various commands (echo, cp, grep, etc.) ● Control statements (if, while, for, etc.) ● Ensure executable permissions (e.g., -rwx r-x r-x) ● Call script using absolute path (e.g.,-/home/userdir/script.bash) ● Calling from the current directory, use ./script.bash
- 8. Example
- 9. If-Then & loop scripts ● If-Then: Conditional execution of code. ● Syntax: `if [ condition ]; then action; fi` ● loop: Repeated execution of code. ● Syntax for 'for' loop: `for i in {start..end}; do action; done`
- 10. Create a shell file and open the nano editor ● Command: nano <file_name> .sh Execution of if-then
- 11. Make the script executable ● Command: chmod +x <file_name> Run the script ● Command: ./<file_name> Note: Since we did not create any such file with the name example.txt so it’s giving the output as File example.txt does not exist
- 12. For loop execution Create a shell file and open it in nano editor ● Command: nano <file_name> .sh
- 13. Make the script executable ● Command: chmod +x <file_name> Run the script ● Command: ./<file_name>
- 14. While loop execution Create a shell file and open it in nano editor ● Command: nano <file_name> .sh
- 15. Make the script executable ● Command: chmod +x <file_name> Run the script ● Command: ./<file_name>
- 16. grep ● Command-line utility used for searching text patterns within files ● Syntax: ● [options]: Optional flags that modify the behavior of grep. ● pattern: The text pattern to search for. ● [file...]: files to search within ● To search for more than one keyword use : egrep –i “keyword|keyword2” file
- 17. grep options ● -i: Ignore case distinctions. ● -n: Display line numbers along with matching lines. ● -l: Display only the names of files containing matches. ● -c: Display count of matching lines ● -o: Show only the matching part of the lines ● -v: Display lines that do not match the pattern ● -w: Match whole words ● -r or -R: Recursively search directories for matching files
- 18. egrep ● Stands for "Global Regular Expressions Print" ● more suitable for complex pattern matching because it allows metacharacters like +, ?, and | without needing to escape them ● can search for multiple patterns in a single command