Commands by soulonfire (3)

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands

Check These Out

Simple complete system backup excluding files or directories
You can exclude more system folders or individual files which are not necessary for the backup and can be recreated after the restore procedure, like /lost+found, /mnt, /media, /tmp, /usr ... Restoring the above backup procedure is as simple as becoming root and typing: $ tar zxpf backup.tgz -C / You can extract any file or directory out of the backup.tgz file for recovery, for instance, if you have a corrupt or mis-configured fstab file, you could simply issue the command: $ tar zxpf backup.tgz /ect/fstab -C / Other options: v add verbose option to see files processed A far safer solution is to restore the desired files under a different directory, and then compare, move, or update the files to their original locations afterward.

Pipe STDOUT to vim
The hyphen tells vim to open from STDOUT - saves having to create temporary files.

List detailed information about a ZIP archive
list zipfile info in long Unix ``ls -l'' format.

Write comments to your history.
A null operation with the name 'comment', allowing comments to be written to HISTFILE. Prepending '#' to a command will *not* write the command to the history file, although it will be available for the current session, thus '#' is not useful for keeping track of comments past the current session.

Check for login failures and summarize
This command checks for the number of times when someone has tried to login to your server and failed. If there are a lot, then that user is being targeted on your system and you might want to make sure that user either has remote logins disabled, or has a strong password, or both. If your output has an "invalid" line, it is a summary of all logins from users that don't exist on your system.

Quick glance at who's been using your system recently
This command takes the output of the 'last' command, removes empty lines, gets just the first field ($USERNAME), sort the $USERNAMES in reverse order and then gives a summary count of unique matches.

Determine next available UID
Typical usage would be in a script that would want the next open UID in a range (in this case 500-600)

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" }

List PCI device with class and vendor/device IDs
This is a quick replacement for lspci if you need to know what's in a given system but pciutils is not installed. You then need something that can look up the IDs from pci.ids if you want the verbose output.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: