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 OPENSOLARIS
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)
Linux Epoch Linux