File Editing and Viewing

Editing and viewing files directly from the command line is a common task in HPC environments. This section covers essential commands and tools for manipulating and examining file contents.

Useful Commands

1. Viewing File Contents

   cat filename

   Outputs the entire contents of the file. Be cautious with large files as this command may cause timeout issues.
   
   

   less filename

   Displays contents of the file one screen/page at a time, allowing for easier navigation through large files.
   
   

   head filename tail filename

   head outputs the first 10 lines of the file by default, while tail displays the last 10 lines. Use -n flag to specify a different number of lines.
   
   

2. Editing Text Files
   
   Editing text files directly from the command line is common in HPC environments. Three main text-editing software are typically available on HPC systems: nano, vim, and emacs. Each editor has its own strengths and learning curve, and many users have their preferred choice based on personal preference and familiarity. To learn more about the differences, see Vim vs. Nano vs. Emacs: Three sysadmins weigh in | Enable Sysadmin (redhat.com).
   
   For detailed instructions on using each editor, please refer to the following links:
   - GNU Nano Documentation
   - Vim Documentation
   - GNU Emacs Documentation
   
   These resources provide comprehensive guides and tutorials to help you get started with your preferred text editor.
   
   

3. Searching Within Files

   Searches for "search-string" within file. If found, grep outputs the line containing "search-string" to the terminal. Use -i for case-insensitive search or -r for recursive search in directories.