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Top Forums Shell Programming and Scripting Please can any one explain this ${0##/} Post 302180965 by unilover on Tuesday 1st of April 2008 03:26:42 PM
Old 04-01-2008
PGM=${0##/}
TMP=/tmp/${PGM}.$$

$0 is the complete-name-of-the-script in side the script (e.g. /home/mydir/myscript.sh)

So, ${0##/} means the complete-name-of-the-script without the starting-slash (if it exists)!!

But, what I thing you wanted to write is:

PGM=${0##*/}

which means complete-name-of-the-script without everthing up to and including the last-slash (e.g. myscript.sh)

Then, $$ is the Process-ID of the current script. So, TMP will be set to be /tmp/myscript.sh.1234 (where 1234 is the process-id).

This combination is normally used to create unique (i.e. different for each running script) names.
 

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The PNM Format(5)						File Formats Manual						 The PNM Format(5)

NAME
pnm - Netpbm superformat DESCRIPTION
The PNM format is just an abstraction of the PBM, PGM, and PPM formats. I.e. the name 'PNM' refers collectively to PBM, PGM, and PPM. The name 'PNM' is an acronym derived from 'Portable Any Map.' This derivation makes more sense if you consider it in the context of the other Netpbm format names: PBM, PGM, and PPM. The more general term 'Netpbm format' refers to the PNM formats plus PAM. PNM is principally used with Netpbm(1) Note that besides being names of formats, PBM, PGM, PPM, and PNM are also classes of programs. A PNM program can take PBM, PGM, or PPM input. That's nothing special -- a PPM program can too. But a PNM program can often produce multiple output formats as well, and a PNM program can see the difference between PBM, PGM, and PPM input and respond to each differently whereas a PPM program sees everything as if it were PPM. This is discussed more in the description of the netpbm programs (1) 'pnm' also appears in the names of the most general Netpbmlibraryroutines(1) , some of which aren't even related to the PNM format. SEE ALSO
ppm(1) , pgm(1) , pbm(1) , pam(1) , programsthatprocessPNM(1) , libnetpbm(1) netpbm documentation 03 October 2003 The PNM Format(5)
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