Replace Text in a File using the Command Line

• How to do an in-file replace using Perl?
  
• How to do an in-file replace using Sed?
  

Replacing Text using Perl:

• If EXTENSION present, rename each file FILE to file FILEEXTENSION.
• Replace text "FROM" with text "TO" everywhere in every FILE.
• Pros: Handles multiple files.
• Cons: May not handle symbolic links the way you want to: Symbolic links will get moved. New file will not be a symbolic link.

• Rename "file1" to "file1.bak".
• Rename "file2" to "file2.bak".
• Replace text "YES" with text "NO" everywhere in both file1 and file2.

Replacing Text using Sed:

• If EXTENSION present, make a backup first by renaming each file FILE to file FILEEXTENSION.
• If --follow-symlinks present, and a file is a symbolic link, follow the link and create the backup in the same directory as the real file, i.e. preserve the symbolic link.
• Replace text "FROM" with text "TO" everywhere in every FILE.
• Pros: Handles multiple files.
• Cons: May not handle symbolic links the way you want to: If --follow-symlinks not present, symbolic links will get moved, and the new file will not be a symbolic link. If --follow-symlinks present, backup files will get created in the same directory as where the target of the link resides.
• Caveats: Will destroy symbolic links if either --follow-symlinks or EXTENSION not present. Sed doesn’t replace overlapping patterns.