Commands by GeckoDH (7)

  • append content of a file to itself

    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


    0
    cat file | tee >> file
    GeckoDH · 2009-07-30 07:34:03 3
  • Break lines after, for example 78 characters, but don't break within a word/string

    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.


    3
    fold -w 78 -s file-to-wrap
    GeckoDH · 2009-05-19 19:33:10 1
  • Share a 'screen'-session

    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.


    13
    screen -x
    GeckoDH · 2009-05-19 19:10:52 2
  • Backup your OpenWRT config (only the config, not the whole system)

    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!)


    3
    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
  • Create variables from a list of names

    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.


    -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
    GeckoDH · 2009-05-19 11:23:00 0
  • Backup with SSH in a archive

    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


    1
    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
  • Validate date, also a date within a leap year

    Important to know: a valid date will return 0, otherwise 1!


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

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Copy all files. All normal files, all hidden files and all files starting with - (minus).
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Convert .flv to .avi

send substituted text to a command without echo, pipe
zsh only - This avoids the need for echo "message" | which creates an entire subshell. Also, the text you are most likely to edit is at the very end of the line, which, in my opinion, makes it slightly easier to edit.

Measures download speed on eth0

list block devices
Shows all block devices in a tree with descruptions of what they are.

open a seperate konsole tab and ssh to each of N servers (konsole 4.2+)
creates a new tab for each of N servers in listofservers.txt and ssh's to said servers then, try the "send to all sessions" feature of konsole to do the same work on all servers at the same time. BIG time saver, but be careful!

Create a new file

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