Running sudo command without password

What I found out is that running a command using sudo without entering password there are two options:

• echo PASSWORD | sudo -S COMMAND
• adding following lineto /etc/sudoers:

username ALL=(ALL) NOPASSWD: COMMAND

Please note that this has to be after all group definitions.
You can check what sudo priviliges you have using

sudo -l

For this case this gives:

(ALL) ALL
(ALL) NOPASSWD: COMMAND 

This means that all command require password except for the COMMAND. If we would put the username definitin before group definitions sudo -l would give:

(ALL) NOPASSWD: COMMAND
(ALL) ALL

This would still require password for all commands.

Find where code was changed in Mercurial

If you want to find out in which revisions a piece of code was changed then you can use a Mercurial command something like this:

hg grep --all PIECE_OF_CODE | awk 'BEGIN {FS=":"} {print $1" "$2}' | uniq

and you will get back a list of files with coresponding revisuin numbers:

repo/src/java/com/kovica/File1.java 30
repo/src/java/com/kovica/File1.java 10

Remove empty lines from a file on Linux using command line

This one is especially useful when searching through Glassfish's log files.
There are many ways you can remove empty lines from a file:

• awk 'NF' file
• sed '/^$/d' file
• grep "^$" -v file
• grep . file
• egrep "^[[:space:]]?$" -v file
• perl -n -e 'print unless /^\s*$/' file

And I'm sure there are many more. :)