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


    0
    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.


    3
    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.


    13
    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!)


    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
  • 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
  • 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
  • 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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Convert seconds to [DD:][HH:]MM:SS
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See a full last history by expanding logrotated wtmp files
When your wtmp files are being logrotated, here's an easy way to unpack them all on the fly to see more than a week in the past. The rm is the primitive way to prevent symlink prediction attack.

Is it a terminal?
Oddly, the isatty(3) glibc C call doesn't have a direct analogue as a command 'isatty(1)'. All is not lost as you can use test(1). For example, your script might be run from a tty or from a GUI menu item but it needs to get user-input or give feedback. Now your script can test STDIN with 'isatty 0' or STDOUT with 'isatty 1' and use xmessage(1) if the tty is not available. The other way to test for this is with 'tty -s' - but that's only for STDIN.

return the latest kernel version from a Satellite / Spacewalk server software channel

GZip all files in a directory separately

Print the detailed statistics of transferred bytes by the firewall rules

Monitor incoming connections of proxies and balancers.
Maybe this will help you to monitor your load balancers or reverse proxies if you happen to use them. This is useful to discover TIME OUTS and this will let you know if one or more of your application servers is not connected by checking.

Set audible alarm when an IP address comes online
I'd rather this one on Gnome, as I'm used to be listening some music while working. I've even created a bash function which receives ADDRESS as parameter.

Convert text to lowercase
Usage: lower [STRING]...

Find unused IPs on a given subnet


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