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Full Discussion: eval in bash
Top Forums Shell Programming and Scripting eval in bash Post 32384 by jetfreggel on Saturday 23rd of November 2002 01:23:15 PM
Old 11-23-2002
eval in bash
hi everyone
i've been reading learning the bash and there is somrthing i don;t
understand what does eval do

i know that it run a command or script twice but i don;t see in
what for cases i can use this

could somebody explain this to me
 

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LEARN ABOUT XFREE86

ldbash

LDBASH(1)							  libbash Manual							 LDBASH(1)

NAME

     ldbash -- Dynamic loader for libbash(7) libraries.

SYNOPSIS

     ldbash [-h | --help]
     ldbash [-l | --list]
     ldbash [-L | --load lib,[lib] ...]
     ldbash [-U | --unload lib,[lib] ...]
     ldbash [-e | --externlist lib,[lib] ...]
     ldbash [--externlist-all]
     ldbash [--i | --internlista lib,[lib] ...]
     ldbash [--internlist-all]

DESCRIPTION

     ldbash  is  used  to  manipulate  libbash(7)  libraries.  Its main function is to load specific library.  It can also print list of available
     libraries, list functions each library exports, unload functions, etc.

     In case of --load and --unload ,the output is intended to be passed to bash eval command.

Options
     -h | --help   Print options summary

     -l | --list   Display list of available libraries. The libraries names listed, may be passed as parameters to other  invocations  of  ldbash.
		   I.e. first you run ldbash --list to see what is available and then you may load it.

     -L | --load lib,[lib] ...
		   Load  given	libraries  -  i.e. print string that should be passed to eval command.	Usually the string contains various source
		   commands.

		   Libraries that given libraries depend on are also loaded.

		   Libraries only loaded if their dependencies are satisfied. Dependencies are resolved using ldbash.cache file, which is  created
		   by ldbashconfig(8).

     -U | --unload lib,[lib] ...
		   Unload given libraries, but not their dependencies.

		   The output should be passed to eval command (in the same manner as with --load ).

     -e | --externlist lib,[lib] ...
		   List all symbols that are exported by given libraries. Symbols are usually functions that given libraries implement.

     --externlist-all
		   List all exported symbols of all available libraries. Symbols are usually functions that library implement.

     -i | --internlist lib,[lib] ...
		   List  all  internal	symbols (i.e. global variables/functions) of given libraries.  This is intended mostly for developers that
		   want to develop library of their own, and want to be sure that they don't override any already defined symbol.

     --internlist-all
		   List all internal symbols of all available libraries.  This is intended mostly for developers that want to develop  library	of
		   their own, and want to be sure that they don't override any already defined symbol.

FILES

     /etc/ldbash.cache
	    Cache  file  that  contains  information  about libraries dependencies and list of exported symbols. See ldbashconfig((8)) for further
	    details.

BUGS

     The script can't load libraries if their file name starts with '-'.  (If someone uses file names that start with a '-' he/she deserves it!)

AUTHORS

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

SEE ALSO

     libbash(7), ldbashconfig(8)

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