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tcpdump sniff pop3,imap,smtp and http

Find duplicate UID in /etc/passwd
You can use only awk

Empty a file
For when you want to flush all content from a file without removing it (hat-tip to Marc Kilgus).

List status of your git repos and let us know if there is any new files to commit.
Source: http://www.bashoneliners.com/oneliners/oneliner/225/

mirrors directory to a ftp server
http://lftp.yar.ru/

Get a regular updated list of zombies
Shows all those processes; useful when building some massively forking script that could lead to zombies when you don't have your waitpid()'s done just right.

resume other user's screen session via su, without pty error
Normally, if you su to another user from root and try to resume that other user's screen session, you will get an error like "Cannot open your terminal '/dev/pts/0' - please check." This is because the other user doesn't have permission for root's pty. You can get around this by running a "script" session as the new user, before trying to resume the screen session. Note you will have to execute each of the three commands separately, not all on the same line as shown here. Credit: I found this at http://www.hjackson.org/blog/archives/2008/11/29/cannot-open-your-terminal-dev-pts-please-check.

Create a backup of the file.
It will create a backup of the filename. The advantage is that if you list the folder the backups will be sorted by date. The command works on any unix in bash.

Copy a folder tree through ssh using compression (no temporary files)
This command will copy a folder tree (keeping the parent folders) through ssh. It will: - compress the data - stream the compressed data through ssh - decompress the data on the local folder This command will take no additional space on the host machine (no need to create compressed tar files, transfer it and then delete it on the host). There is some situations (like mirroring a remote machine) where you simply cant wait for a huge time taking scp command or cant compress the data to a tarball on the host because of file system space limitation, so this command can do the job quite well. This command performs very well mainly when a lot of data is involved in the process. If you copying a low amount of data, use scp instead (easier to type)

send a circular
don't need echo :P


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