Commands by QNimbus (1)

What's this? 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.

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Count lines in a file with grep
Returns the number of lines in a file, emulates "wc -l" behavior with grep.

give a binary the ability to open ports below 1024 as non root user
Binding a server to privileged port on Linux w/o running as root This is applicable to any service using privileged ports (< 1024), for instance to run a HTTP server on port 80 or a LDAP directory server on port 389 for example.

unrar all part1 files in a directory

Check variable has been set

Check reverse DNS
I'm just a simple programmer. I find dig too verbose. host tells me alias(es) and IP address in a quick to grok format with nothing special to remember for input parameters. With thanks to

Script executes itself on another host with one ssh command
Now put more interesting stuff on the script in replacement of hostname, even entire functions, etc, and stuff. hosta> cat #!/bin/sh [ $1 == "client" ] && hostname || cat $0 | ssh $1 /bin/sh -s client hosta> hostb hostb hosta>

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"

Rotate all jpeg images in current folder, rename them to EXIF datetime and set files timestamp to EXIF datetime

Generate a ZenCart-style MD5 password hash.
ZenCart uses a MD5 with a salt to secure its passwords. If you need to forcibly change someone's password to a known value within the database, this one-liner can generate the password. Change the value of 'p' to the password you want.

Functions to display, save and restore $IFS
You can display, save and restore the value of $IFS using conventional Bash commands, but these functions, which you can add to your ~/.bashrc file make it really easy. To display $IFS use the function ifs shown above. In the sample output, you can see that it displays the characters and their hexadecimal equivalent. This function saves it in a variable called $saveIFS: $ sifs () { saveIFS=$IFS; } Use this function to restore it $ rifs () { IFS=$saveIFS; } Add this line in your ~/.bashrc file to save a readonly copy of $IFS: $ declare -r roIFS=$IFS Use this function to restore that one to $IFS $ rrifs () { IFS=$roIFS; }

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