Linux - Displaying a file without the commentary lines

It may be needed to view a file without displaying the numerous commentary lines attached to it (especially for the configuration files of your OS) and also considering removal of the empty lines.

Grep

• Making use of "egrep" (or "grep-E"):

  • egrep -v '^(#|$)'  /etc/samba/smb.conf 

  • grep -E -v '^(#|$)'  /etc/samba/smb.conf

• Lines starting with a hash (#) or the ending symbol dollar($) shall not be displayed.
• In this case the delimiter comment is not placed at the start of line but behind (space or tab), but you can change your expression as follows:

  • grep -E -v '^(#|;|$|[ ]*#)' /etc/samba/smb.conf

Sed

• Making use of sed

  • sed -e '/^[ ]*#/d' -e '/^$/d' /etc/samba/smb.conf

• Here it removes firstly, lines begining with a space or a pound sign, then removes all blank lines.
• You can improve the expression like:

  • sed -e '/^[ ]*#/d' -e '/^[ ]*;/d' -e '/^$/d' /etc/samba/smb.conf

Perl

• Making use of perl.
• Making use of perl will imply,considering the implementation of regex based on the engine used by the utilities.
• Using the NFA (Nondeterministic Finite Automation) engine, though slower than DFA (Deterministic Finite Automation) engine,allows you to refine and manage the regex to get a specific result:

  • perl -ne 'print unless /^\s*[;\$#]|^$/' file_config