Linux / UNIX View Only Configuration File Directives ( Uncommented Lines of a Config File )

Author: Vivek Gite Last updated: May 3, 2017 8 comments

Most Linux and UNIX-like system configuration files are documented using comments, but some time I just need to see line of configuration text in a config file. How can I view just the uncommented configuration file directives from squid.conf or httpd.conf file? How can I strip out comments and blank lines on a Linux or Unix-like systems?

To view just the uncommented lines of text in a config file[donotprint]

Tutorial details
Difficulty	Easy (rss)
Root privileges	No
Requirements	grep/egrep/sed
Time	1m

[/donotprint] use the grep, sed, awk, perl or any other text processing utility provided by UNIX / BSD / OS X / Linux operating systems.

grep command example to strip out command

You can use the gerp command as follows:
$ grep -v "^#" /path/to/config/file $ grep -v "^#" /etc/apache2/apache2.conf
Sample outputs:

ServerRoot "/etc/apache2"
 
LockFile /var/lock/apache2/accept.lock
 
PidFile ${APACHE_PID_FILE}
 
Timeout 300
 
KeepAlive On
 
MaxKeepAliveRequests 100
 
KeepAliveTimeout 15
 
 
<IfModule mpm_prefork_module>
    StartServers          5
    MinSpareServers       5
    MaxSpareServers      10
    MaxClients          150
    MaxRequestsPerChild   0
</IfModule>
 
<IfModule mpm_worker_module>
    StartServers          2
    MinSpareThreads      25
    MaxSpareThreads      75 
    ThreadLimit          64
    ThreadsPerChild      25
    MaxClients          150
    MaxRequestsPerChild   0
</IfModule>
 
<IfModule mpm_event_module>
    StartServers          2
    MaxClients          150
    MinSpareThreads      25
    MaxSpareThreads      75 
    ThreadLimit          64
    ThreadsPerChild      25
    MaxRequestsPerChild   0
</IfModule>
 
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}
 
 
AccessFileName .htaccess
 
<Files ~ "^\.ht">
    Order allow,deny
    Deny from all
    Satisfy all
</Files>
 
DefaultType text/plain
 
 
HostnameLookups Off
 
ErrorLog /var/log/apache2/error.log
 
LogLevel warn
 
Include /etc/apache2/mods-enabled/*.load
Include /etc/apache2/mods-enabled/*.conf
 
Include /etc/apache2/httpd.conf
 
Include /etc/apache2/ports.conf
 
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined
LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %O" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent
 
CustomLog /var/log/apache2/other_vhosts_access.log vhost_combined
 
 
 
Include /etc/apache2/conf.d/
 
Include /etc/apache2/sites-enabled/

To suppress blank lines use egrep command, run:

egrep -v "^#|^$" /etc/apache2/apache2.conf
## or pass it to the page such as more or less ##
egrep -v "^#|^$" /etc/apache2/apache2.conf | less
 
## Bash function ######################################
## or create function or alias and use it as follows ##
## viewconfig /etc/squid/squid.conf                  ##
#######################################################
viewconfig(){
   local f="$1"
   [ -f "$1" ] && command egrep -v "^#|^$" "$f" || echo "Error $1 file not found."
}

Sample output:

Fig.01: Unix/Linux Egrep Strip Out Comments Blank Lines

Understanding grep/egrep command line options

The -v option invert the sense of matching, to select non-matching lines. This option should work under all posix based systems. The regex ^$ matches and removes all blank lines and ^# matches and removes all comments that starts with a “#”.

sed Command example

GNU / sed command can be used as follows:
$ sed '/ *#/d; /^ *$/d' /path/to/file $ sed '/ *#/d; /^ *$/d' /etc/apache2/apache2.conf
GNU or BSD sed can update your config file too. The syntax is as follows to edit files in-place, saving backups with the specified extension such as .bak:

sed -i'.bak.2015.12.27' '/ *#/d; /^ *$/d' /etc/apache2/apache2.conf

For more info see man pages – sed(1)

This entry is 7 of 7 in the Linux / UNIX grep Command Tutorial series. Keep reading the rest of the series:

How To Use grep Command In Linux / UNIX
Regular Expressions In grep
Search Multiple Words / String Pattern Using grep Command
Grep Count Lines If a String / Word Matches
Grep From Files and Display the File Name
How To Find Files by Content Under UNIX
grep command: View Only Configuration File Directives

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