Bash Snippet: Print a config file without comments

Published on April 23, 2019 1 minute

Logging in on a server, printing a configuration file and trying to find the relevant setting from thousands of comment lines. Sounds familiar?

Not that comments are useless in a configuration file but sometimes it’s handy to print a configuration file without the comment lines. Especially when the file is thousand lines long but the useful lines fit the twenty five lines of a standard terminal.

The egrep command which is standard on most Linux distributions and on MacOS, can strip out the unwanted lines:

egrep -v '^\s*(#|$)' /etc/ssh/sshd_config

The -v switch prints out the lines that do not match the given regex ^\s*(#|$). And this regex captures:

empty lines
lines with only whitespaces
lines that contains only comments

And now, your active sshd configuration fits a 25 lines terminal!

$ egrep -v '^\s*(#|$)'  /etc/ssh/sshd_config
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
SyslogFacility AUTHPRIV
PermitRootLogin no
AuthorizedKeysFile	.ssh/authorized_keys
PasswordAuthentication no
ChallengeResponseAuthentication no
GSSAPIAuthentication yes
GSSAPICleanupCredentials no
UsePAM yes
X11Forwarding yes
UseDNS no
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS
Subsystem	sftp	/usr/libexec/openssh/sftp-server