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Full Discussion: Can I use a variable with brace expansion?
Top Forums UNIX for Dummies Questions & Answers Can I use a variable with brace expansion? Post 302544038 by DeCoTwc on Tuesday 2nd of August 2011 06:38:49 PM
Old 08-02-2011
Can I use a variable with brace expansion?
So, I was bored on the train today, and was thinking of ways to loop through elements of an array. I came up with the following simple script, but it doesn't work as brace expansion doesn't seem to work with variables. Is there something I'm missing, or does the shell just not work like this?

Code:
(18:33:24\[D@DeCoWork15)
[~]$ cat prac.sh
#!/bin/bash

x=(aa bb cc dd ee ff gg hh ii jj kk ll mm nn oo pp qq rr ss tt uu vv ww xx  yy zz)
CAP=${#x[*]}
echo $CAP
for i in {1..$CAP};do echo ${x[${i}]};done

(18:35:19\[D@DeCoWork15)
[~]$ bash prac.sh
26
prac.sh: line 6: {1..26}: syntax error: operand expected (error token is "{1..26}")

So, clearly it is recognizing the variable, but it's not expanding the 1..26. Any thoughts?

Also, I'm aware that this will leave me with the issue that I'm expanding 1-26 when what I really want is 0-25...but I'll burn that bridge later.
 

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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)

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