Scripting Question (For Loop) Post: 302953021

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Top Forums UNIX for Dummies Questions & Answers Scripting Question (For Loop) Post 302953021 by neutronscott on Tuesday 25th of August 2015 01:36:49 AM

08-25-2015

Registered User

Quote:

Originally Posted by shah9250

However, what do you mean by properly split list of files?

See the following shell session example:

Code:

mute@tiny:~$ mkdir shah9250
mute@tiny:~$ cd shah9250/
mute@tiny:~/shah9250$ touch 'file with spaces'
mute@tiny:~/shah9250$ for f in $(ls); do echo "work on [$f]"; done
work on [file]
work on [with]
work on [spaces]
mute@tiny:~/shah9250$ for f in *; do echo "work on [$f]"; done
work on [file with spaces]

We know there is only one file and the loop should only be called once, but with that use of $(ls) it's not. Quoting and word splitting are the toughest parts of learning the shell, in my opinion. Once that clicks things are much easier.

Quote:

Originally Posted by shah9250

Also what is a glob? Also you used a wildcard (*) in the "for" statement, so how does the variable $file receive input?

Glob is filename expansion. * is a wildcard that matches anything. You can simply do echo * or echo *.txt to show all files or all files ending in .txt. My meaning wasn't to distract from the for loop, just for down the road you'll want to use best practices. Filenames can contain any character except the NUL character and the path delimiter / and a great deal of care must be taken to make robust scripts.

I cannot recommend Greg's wiki enough. The bash guide on the site is excellent value for the price: BashGuide - Greg's Wiki

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LEARN ABOUT POSIX

libbash

LIBBASH(7)							  libbash Manual							LIBBASH(7)

NAME

     libbash -- A bash shared libraries package.

DESCRIPTION

     libbash  is  a package that enables bash dynamic-like shared libraries. Actually its a tool for managing bash scripts whose functions you may
     want to load and use in scripts of your own.

     It contains a 'dynamic loader' for the shared libraries ( ldbash(1)), a configuration tool (ldbashconfig(8)), and some libraries.

     Using ldbash(1) you are able to load loadable bash libraries, such as getopts(1) and hashstash(1).  A bash shared library that can be  loaded
     using
     ldbash(1) must answer 4 requirments:

     1.     It must be installed in $LIBBASH_PREFIX/lib/bash (default is /usr/lib/bash).

     2.     It must contain a line that begins with '#EXPORT='.  That line will contain (after the '=') a list of functions that the library
	    exports.  I.e. all the function that will be usable after loading that library will be listed in that line.

     3.     It must contain a line that begins with '#REQUIRE='.  That line will contain (after the '=') a list of bash libraries that are
	    required for our library.  I.e. every bash library that is in use in our bash library must be listed there.

     4.     The library must be listed (For more information, see ldbashconfig(8)).

   Basic guidelines for writing library of your own:
     1.     Be aware, that your library will be actually sourced. So, basically, it should contain (i.e define) only functions.

     2.     Try to declare all variables intended for internal use as local.

     3.     Global variables and functions that are intended for internal use (i.e are not defined in '#EXPORT=') should begin with:
		  __<library_name>_
	    For example, internal function myfoosort of hashstash library should be named as
		  __hashstash_myfoosort
	    This helps to avoid conflicts in global name space when using libraries that come from different vendors.

     4.     See html manual for full version of this guide.

AUTHORS

     Hai Zaar <haizaar@haizaar.com>
     Gil Ran <ril@ran4.net>

SEE ALSO

     ldbash(1), ldbashconfig(8), getopts(1), hashstash(1) colors(1) messages(1) urlcoding(1) locks(1)

Linux								       Epoch								     Linux