meaning of ${0%${0##*/}} Post: 302238841

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Operating Systems AIX meaning of ${0%${0##*/}} Post 302238841 by bakunin on Monday 22nd of September 2008 06:51:17 AM

09-22-2008

Registered User

Quote:

Originally Posted by nyelavarthy

. ${0%${0##*/}}Script2 or . ./Script2

Both do the same job. then why use this ". ${0%${0##*/}}Script2" instead of simply using ". ./Script2"?

In this case they expand to the same value, but that has not always to be the case. Suppose the following: you call your script not from the directory where it is stored but from somewhere else:

Code:

$ cd /some/dir
$ /some/other/dir/script
$ _

inside your script the "./" will expand to the PWD, which is not where the script is stored but where you have been when starting the script - "/some/dir" in the example, not "/some/other/dir". If you now execute

Code:

. ./script2

you will execute "/some/dir/script2" instead of "/some/other/dir/script2". Still $0 will contain "/some/other/dir/script" and subsequently the expansion will find script2 on its correct place.

As a rule of thumb: avoid relative paths like the plague in scripts. Always use absolute paths to make sure you end up where you suppose to end up.

I hope this helps

bakunin

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shtool-mkshadow

SHTOOL-MKSHADOW.TMP(1)					      GNU Portable Shell Tool					    SHTOOL-MKSHADOW.TMP(1)

NAME

       shtool-mkshadow - GNU shtool create shadow tree using symlinks

SYNOPSIS

       shtool mkshadow [-v|--verbose] [-t|--trace] [-a|--all] src-dir dst-dir

DESCRIPTION

       This command creates a shadow tree of src-dir under dst-dir by recreating the directory hierarchy of src-dir under dst-dir and by creating
       the files of src-dir by linking them into the corresponding directories under dst-dir via symbolic links. When src-dir can be reached via
       relative paths from dst-dir, relative symbolic links are used, too. This high-level functionality is originally designed for developers to
       create copies of source trees.

OPTIONS

       The following command line options are available.

       -v, --verbose
	   Display some processing information.

       -t, --trace
	   Enable the output of the essential shell commands which are executed.

       -a, --all
	   Really shadow all files and directories in src-dir. Default is to skip CVS related files and directories, backup files, object files,
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EXAMPLE

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HISTORY

       The GNU shtool mkshadow command was originally written by Ralf S.  Engelschall <rse@engelschall.com> in 1998 for Apache. It was later
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SEE ALSO

       shtool(1), ln(1).

18-Jul-2008							   shtool 2.0.8 					    SHTOOL-MKSHADOW.TMP(1)

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