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Top Forums Shell Programming and Scripting Function prototype declaration Post 302866627 by Corona688 on Tuesday 22nd of October 2013 12:40:37 PM
Old 10-22-2013
Quote:
Originally Posted by Balasankar
Isn't possibe to decare prototype kind of statement as we do in C++ ?
Nope.

C++ can do that because it's a compiled language. It can assume that "okay, there's a function named xyzzy, I can find its contents later". When the program gets linked together into an exe, it has to actually go find all these libraries to do so.

Shell language runs immediately with no compilation step. If those functions don't already exist, they don't exist. (A few shells might have special features here. These features do not exist in general.)

Even C++ can't manage if you don't tell it what the functions actually are though! At the very least you have to #include <something> before you use them, for it to even assume they exist. You can do something like #include in shell. Put your function, or a bunch of functions, in another file then do this:

Code:
. /path/to/script-name

Note the space between the dot and everything else, that's essential.

script-name will be run in your current shell, effectively loading the functions in it.
 

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SHELL-QUOTE(1)						User Contributed Perl Documentation					    SHELL-QUOTE(1)

NAME
shell-quote - quote arguments for safe use, unmodified in a shell command SYNOPSIS
shell-quote [switch]... arg... DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands or files with embedded white space or shell globbing characters safely. Here are a few examples. EXAMPLES
ssh preserving args When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and passes them to "$SHELL -c". This doesn't work as intended: ssh host touch 'hi there' # fails It creates 2 files, hi and there. Instead, do this: cmd=`shell-quote touch 'hi there'` ssh host "$cmd" This gives you just 1 file, hi there. process find output It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote: eval set -- `find -type f -print0 | xargs -0 shell-quote --` debug shell scripts shell-quote is better than echo for debugging shell scripts. debug() { [ -z "$debug" ] || shell-quote "debug:" "$@" } With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can. save a command for later shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are things the user can't pass through), you can do something like this: user_switches= while [ $# != 0 ] do case x$1 in x--pass-through) [ $# -gt 1 ] || die "need an argument for $1" user_switches="$user_switches "`shell-quote -- "$2"` shift;; # process other switches esac shift done # later eval "shell-quote some-command $user_switches my args" OPTIONS
--debug Turn debugging on. --help Show the usage message and die. --version Show the version number and exit. AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions. AUTHOR
Roderick Schertler <roderick@argon.org> perl v5.16.3 2010-06-11 SHELL-QUOTE(1)
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