Commands using fetchmail (2)

  • Print multiline text starting and ending at specific regexps with perl

    Using perl, here, we grep the man page of fetchmail to find the paragraph starting with '-k | --keep' and ending before the paragraph starting with '-K | --nokeep' Show Sample Output


    0
    man fetchmail | perl -ne 'undef $/; print $1 if m/^.*?(-k \| --keep.*)-K \| --nokeep.*$/smg'
    unixmonkey4437 · 2009-06-25 23:51:35 0
  • Start delivery of mail queued on a secondary mail server.

    This uses fetchmail to issue an etrn command that causes the MTA on the secondary mail server to process the queue for the specified domain. You can also just use telnet or nc to connect to port 25 of the server and then: etrn yourdomain.example.org 250 2.0.0 Queuing for node yourdomain.example.org started Show Sample Output


    0
    fetchmail -p etrn --fetchdomains yourdomain.example.org secondary-server.example.org
    jasonjgw · 2010-11-20 23:38:09 0

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invoke MATLAB functions from command line
`-r script.m` also possible

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

Get the full path to a file
Useful in scripts when the file is passed in as an argument. Eg. $ filepath=$(realpath $1)

Configure second monitor to sit to the right of laptop
You'll need to make sure your xorg.conf permits a virtual screen size this big. If it doesn't then xrandr should return a suitable error message that tells you the required size.

Redirect a filehandle from a currently running process.
This command uses the debugger to attach to a running process, and reassign a filehandle to a file. The two commands executed in gdb are p close(1) which closes STDOUT and p creat("/tmp/filename",0600) which creates a file and opens it for output. Since file handles are assigned sequentially, this command opens the file in place of STDOUT and once the process continues, new output to STDOUT will instead be written to our capture file.

swap stdout and stderr
Possible use, to filter something in stderr: (/usr/bin/$COMMAND $PARAM 3>&1 1>&2 2>&3 | grep -v $uninteresting_error ) 3>&1 1>&2 2>&3

Count items in JSON array
Pipe any JSON to jq, then count with the appropiate expression and use the | length on the array

commandline dictionary
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Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Remove all backup files in my home directory
I use this simple command for remove all backup files generated usually by editors like Vim and Emacs.

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