Commands by GeckoDH (7)

  • The command `cat file >> file` failes with the following error message: cat: file: input file is output file `tee` is a nice workaround without using any temporary files. Show Sample Output

    cat file | tee >> file
    GeckoDH · 2009-07-30 07:34:03 3
  • Per default, linux/unix shells are configured with a width of 80 characters. If you like to edit a phrase or string on a line with more than 80 characters it might take long to go there (for example a line with 1000 characters and you like to edit the 98th word which is character 598-603). Maybe you might wish to use 78 characters, because if you forward the text via mail and the text will be quoted (2 extra characters at the beginning to the line "> "), you use 80 characters, otherwise 82, which are lame.

    fold -w 78 -s file-to-wrap
    GeckoDH · 2009-05-19 19:33:10 1
  • Ater person A starts his screen-session with `screen`, person B can attach to the srceen of person A with `screen -x`. Good to know, if you need or give support from/to others.

    screen -x
    GeckoDH · 2009-05-19 19:10:52 2
  • You only have to fill in your administrative account and password, and the router FQDN! I recommand to execute this command not over the internet, because there is no encryption (the username and password will be transmitted in plaintext!)

    curl -d 'username=root&password=your-good-password' "http://router/cgi-bin/luci/admin/system/backup?backup=kthxbye" > `date +%Y%d%m`_config_backup.tgz
    GeckoDH · 2009-05-19 11:32:30 1
  • VARNAMES='ID FORENAME LASTNAME ADDRESS CITY PHONE MOBILE MAIL ...' cat customer.csv | while read LINE ; do COUNT=1 for VAR in $VARNAMES ; do eval "${VAR}=`echo $LINE | /usr/bin/awk {'print $'$COUNT''}`" let COUNT=COUNT+1 done done Maybe you have a CSV-File with addresses, where you have to process each contact (one per line, write each value to own variable). Of course you can define every variable, but this way is more simple and faster (to write). VARNAMES includes the variable names. Pay attention: the number of names in VARNAMES have to be the same than in the CSV-file the fields. If the CSV is not seperated with ";", you can set the seperator after the awk-binary with -F"_" for example.

    VARNAMES='ID FORENAME LASTNAME ADDRESS CITY PHONE MOBILE MAIL' ; cat customer.csv | while read LINE ; do COUNT=1 ; for VAR in $VARNAMES ; do eval "${VAR}=`echo $LINE | /usr/bin/awk {'print $'$COUNT''}`" ; let COUNT=COUNT+1 ; done ; done
    GeckoDH · 2009-05-19 11:23:00 0
  • PRIVATEKEY - Of course the full path to the private key \n HOST - The host where to get the backup \n SOURCE - The directory you wish to backup \n DESTINATION - The destination for the backup on your local machine

    ssh -i $PRIVATEKEY $HOST -C 'cd $SOURCE; tar -cz --numeric-owner .' | tee $DESTINATION/backup.tgz | tar -tz
    GeckoDH · 2009-05-18 20:36:45 0
  • Important to know: a valid date will return 0, otherwise 1!

    date -d2009-05-18 > /dev/null 2>&1 ; echo $?
    GeckoDH · 2009-05-18 20:30:05 0

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Selecting a random file/folder of a folder
Also looks in subfolders

Kill all processes that don't belong to root/force logoff
explanation: grep -- displays process ids -v -- negates the matching, displays all but what is specified in the other options -u -- specifies the user to display, or in this case negate The process loops through all PIDs that are found by pgrep, then orders a forced kill to the processes in numerical order, effectively killing the parent processes first including the shells in use which will force the users to logout. Tested on Slackware Linux 12.2 and Slackware-current

Add fade in/out to first & last 25 frames of a video
Replace vid.mp4 with the path to your original video file, and out.mp4 to the path where you want to save the new file. To view the output first before saving, remove "-consumer avformat:out.mp4" from the end. Documentation for mlt framework and melt command can be found here:

Install pip with Proxy
Installs pip packages defining a proxy

Silently deletes lines containing a specific string in a bunch of files
This command will find all occurrences of one or more patterns in a collection of files and will delete every line matching the patterns in every file

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"

Numeric zero padding file rename
rename file name with fixed length nomeric format pattern

Inserts the results of an autocompletion in the command line
Pressing ESC then * will insert in the command line the results of the autocompletion. It's hard to explain but if you look the sample output or do $ echo ESC * you will understand quickly. By the way, few reminders about ESC : - Hold ESC does the same thing as tab tab - 'ESC .' inserts the last argument of last command (can be done many times in order to get the last argument of all previous commands)

Makes the permissions of file2 the same as file1
Also works with: $chgrp --reference file1 file2 $chown --reference file1 file2

make, or run a script, everytime a file in a directory is modified

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