Commands by clockworkavian (4)

  • This will perform one of two blocks of code, depending on the condition of the first. Essentially is a bash terniary operator. To tell if a machine is up: ping -c1 machine { echo succes;} || { echo failed; } Because of the bash { } block operators, you can have multiple commands ping -c1 machine && { echo success;log-timestamp.sh }|| { echo failed; email-admin.sh; } Tips: Remember, the { } operators are treated by bash as a reserved word: as such, they need a space on either side. If you have a command that can fail at the end of the true block, consider ending said block with 'false' to prevent accidental execution Show Sample Output


    23
    true && { echo success;} || { echo failed; }
    clockworkavian · 2009-04-02 01:49:25 13
  • Not so much handy by itself, but very nice in shell scripts. This makes you a handy ncurses based checklist. Much like terminal installers, just use the arrow keys and hit 'Space' to adjust the selections. Returns all selected tags as strings, with no newline at the end. So, your output will be something like: "one" "two" "three" "four" "etc" For those who prefer bash expansion over gratuitious typing: whiptail --checklist "Simple checkbox menu" 12 35 3 $(echo {one,two,three,four}" '' 0"} ) Things to note: The height must includes the outer border and padding: add 7 to however many items you want to show up at the same time. If the status is 1, it will be selected by default. anything else, will be deselected. Show Sample Output


    6
    whiptail --checklist "Simple checkbox menu" 11 35 5 tag item status repeat tags 1
    clockworkavian · 2009-03-30 12:21:48 8
  • This function runs a program in the background, and logs all output to an automatically created logfile. That way, you can still get at the output without it clogging up your terminal. Tip: Throw fork() and this: for prog in firefox kate konqueror ;do alias $prog="fork $prog";done into your bashrc, so that they'll automatically run out of the way. Show Sample Output


    1
    function fork () { tf=$(tempfile -d /tmp -p $1.);echo -n "$tf "; $@ &>$tf& }
    clockworkavian · 2009-03-25 23:33:54 7
  • Depending on the network setup, you may not get the hostname. Show Sample Output


    4
    nmap 192.168.0-1.0-255 -sP
    clockworkavian · 2009-03-23 22:19:05 10

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Limit bandwidth usage by any program
Trickle is a voluntary, cooperative bandwidth shaper. it works entirely in userland and is very easy to use. The most simple application is to limit the bandwidth usage of programs.

Get your external IP address
Yeah I know it's been up here a million times, but this service is a really clean and nice one. Nothing but your IP address on it. Actually I was to write something like this, and noticed this on appspot... ;)

Generate binary sequence data

Use md5sum to check your music and movie files. Also use diff.
This is a beginning script. You can create a file with > filename. You can also use diff to compare output run at different times to verify no change in your files. I apologize in advance if this is too simple. For some it should be a start.

Colored cal output

Repeatedly send a string to stdout-- useful for going through "yes I agree" screens

from the console, start a second X server
This starts a very basic X session, with just a simple xterm. You can use this xterm to launch your preferred distant session. $ ssh -X john@otherbox gnome-session Try also startkde or fluxbox or xfce4-session. To switch between your two X servers, use CTRL+ALT+F7 and CTRL+ALT+F8.

find out how much space are occuipied by files smaller than 1024K
The command gives size of all files smaller than 1024k, this information, together with disk usage, can help determin file system parameter (e.g. block size) or storage device (e.g. SSD v.s. HDD). Note if you use awk instead of "cut| dc", you easily breach maximum allowed number of records in awk.

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Verify/edit bash history command before executing it
Bash history commands are those that begin with the character ! (eg. the most popular 'sudo !!' Explained here => http://www.commandlinefu.com/commands/view/13). By default bash immediately executes the history command. Setting this shell option will make bash first allow you to verify/edit an history command before executing it. To set this option permanently, put this command in ~/.profile or ~/.bashrc file. To unset this option issue following command. $shopt -u histverify


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