Linux - Displaying a file without the commentary lines

April 2018

Grep
Sed
Perl

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
```

Published by jak58. Latest update on August 26, 2010 at 08:10 AM by jak58.

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Linux - Displaying a file without the commentary lines

Grep

Sed

Perl

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