Commands by RossRewer (0)

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Use the builtin ':' bash command to increment variables
I just found another use for the builtin ':' bash command. It increments counters for me in a loop if a certain condition is met... : [arguments] No effect; the command does nothing beyond expanding arguments and performing any specified redirections. A zero exit code is returned.

Do a search-and-replace in a file after making a backup

delete all trailing whitespace from each line in file

subtraction between lines
It's allways strange for me to see sed and awk in the same command line if you can avoid it

Shows what processes need to be restarted after system upgrade
This command can be installed in debian by the package debian-goodies. It also outputs the /etc/init.d/ commands that you need to do.

Generate diff of first 500 lines of two files
Useful for massive files where doing a full diff would take too long. This just runs diff on the first 500 lines of each. The use of subshells to feed STDIN is quite a useful construct.

Edit a script that's somewhere in your path.
Often I need to edit a bash or perl script I've written. I know it's in my path but I don't feel like typing the whole path (or I don't remember the path).

Delete recursively only empty folders on present dir

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)
Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

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