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 CSV to JSON
Replace 'csv_file.csv' with your filename.

Generate 2000 images with its number written on it

Discovering all open files/dirs underneath a directory
It may be helpful in case you need to umount a directory and some process is preventing you to do so keeping the folder busy. The lsof may process the +D option slowly and may require a significant amount of memory because it will descend the full dir tree. On the other hand it will neither follow symlinks nor other file systems.

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

Set laptop display brightness
Run as root. Path may vary depending on laptop model and video card (this was tested on an Acer laptop with ATI HD3200 video). $ cat /proc/acpi/video/VGA/LCD/brightness to discover the possible values for your display.

Add page numbers to a PDF
Put this code in a bash script. The script expects the PDF file as its only parameter. It will add a header to the PDF containing the page numbers and output it to a file with the suffix "-header.pdf" Requires enscript, ps2pdf and pdftk.

execute a shell with netcat without -e
Shorter version with proper stderr redirection .

Update twitter via curl
Doesn't require password (asks for it instead)

Write comments to your history.
A null operation with the name 'comment', allowing comments to be written to HISTFILE. Prepending '#' to a command will *not* write the command to the history file, although it will be available for the current session, thus '#' is not useful for keeping track of comments past the current session.

is today the end of the month?


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