Commands using grep (1,935)

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Redirect incoming traffic to SSH, from a port of your choosing
Stuck behind a restrictive firewall at work, but really jonesing to putty home to your linux box for some colossal cave? Goodness knows I was...but the firewall at work blocked all outbound connections except for ports 80 and 443. (Those were wide open for outbound connections.) So now I putty over port 443 and have my linux box redirect it to port 22 (the SSH port) before it routes it internally. So, my specific command would be: $iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-ports 22 Note that I use -A to append this command to the end of the chain. You could replace that with -I to insert it at the beginning (or at a specific rulenum). My linux box is running slackware, with a kernel from circa 2001. Hopefully the mechanics of iptables haven't changed since then. The command is untested under any other distros or less outdated kernels. Of course, the command should be easy enough to adapt to whatever service on your linux box you're trying to reach by changing the numbers (and possibly changing tcp to udp, or whatever). Between putty and psftp, however, I'm good to go for hours of time-killing.

Batch convert PNG to JPEG
Convert all PNG images in directory to JPEG using ImageMagick, and delete the old PNG images.

seconds since epoch to ISO timestamp
No need to use perl, awk, nor /usr/bin/date -- bash's "printf" builtin will do it.

Create subdirectory and move files into it
With this form you dont need to cut out target directory using grep/sed/etc.

Copy from host 1 to host 2 through your host

one-liner mpc track changer using dmenu
Add a [fluxbox] binding in your key file then this command provides a dmenu selector for the next track to play

Find out how old a web page is
I used to use the Firefox "View page info" feature a lot to determine how stale the web page I was looking at was. Now that I use mostly Chrome I miss that feature, so here is a command line alternative using wget. The -S says to display the server response, the --spider says to not download any files/pages, just fetch the header. The output goes to stderr, so to grep it you use 2>&1 to combine the stderr stream with stdout, the pipe that to grep for Last-Modified. You can use curl instead if you have it installed, like this: $ curl --head -s http://osswin.sourceforge.net | grep Mod

sort list of email addresses by domain.tld
email random list can be created here: https://www.randomlists.com/email-addresses

get a random 0/1, use it for on/off, yes/no
use it to add a random boolean switch to your script

List only directories, one per line
omit the 1 (one) if you don't need one-per-line


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