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Top Forums Shell Programming and Scripting Blog-Thread: Creating a Shell Wrapper and Runtime Modifier (SWARM) Post 303045307 by drl on Monday 16th of March 2020 07:10:46 AM
Old 03-16-2020
Hi.

Perhaps I missed something, but variables are created/set when from a function:
Code:
#!/usr/bin/env bash

# @(#) s1       Demonstrate use of option "-g" in "declare".

LC_ALL=C ; LANG=C ; export LC_ALL LANG
pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
em() { pe "$*" >&2 ; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
C=$HOME/bin/context && [ -f $C ] && $C

(
        declare -g my_test_a="a test"
        export my_test_b="an exported beer"
)

unset my_test_a my_test_b
pl " Results, not in function:"
echo $my_test_a
echo $my_test_b

f1 ()
{
    declare -g my_test_a="a test"
    export my_test_b="an exported beer"
}

unset my_test_a my_test_b
pl " Results, in function f1:"
f1
echo $my_test_a
echo $my_test_b

exit

producing:
Code:
$ ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 3.16.0-7-amd64, x86_64
Distribution        : Debian 8.11 (jessie) 
bash GNU bash 4.3.30

-----
 Results, not in function:



-----
 Results, in function f1:
a test
an exported beer

Seen in man bash:
Quote:
-g create global variables when used in a shell function; otherwise
ignored
and noted with shellcheck:
Code:
...
In s1 line 21:
echo $my_test_a
     ^-- SC2031: my_test_a was modified in a subshell. That change might be lost. 
...

Apologies if I missed it ... cheers, drl

( currently listening: Bartok: String Quartets, but soon Yes )
This User Gave Thanks to drl For This Post:
 

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WHICH(1)						      General Commands Manual							  WHICH(1)

NAME
which - shows the full path of (shell) commands. SYNOPSIS
which [options] [--] programname [...] DESCRIPTION
Which takes one or more arguments. For each of its arguments it prints to stdout the full path of the executables that would have been exe- cuted when this argument had been entered at the shell prompt. It does this by searching for an executable or script in the directories listed in the environment variable PATH using the same algorithm as bash(1). This man page is generated from the file which.texinfo. OPTIONS
--all, -a Print all matching executables in PATH, not just the first. --read-alias, -i Read aliases from stdin, reporting matching ones on stdout. This is useful in combination with using an alias for which itself. For example alias which='alias | which -i'. --skip-alias Ignore option `--read-alias', if any. This is useful to explicity search for normal binaries, while using the `--read-alias' option in an alias or function for which. --read-functions Read shell function definitions from stdin, reporting matching ones on stdout. This is useful in combination with using a shell func- tion for which itself. For example: which() { declare -f | which --read-functions $@ } export -f which --skip-functions Ignore option `--read-functions', if any. This is useful to explicity search for normal binaries, while using the `--read-functions' option in an alias or function for which. --skip-dot Skip directories in PATH that start with a dot. --skip-tilde Skip directories in PATH that start with a tilde and executables which reside in the HOME directory. --show-dot If a directory in PATH starts with a dot and a matching executable was found for that path, then print "./programname" rather than the full path. --show-tilde Output a tilde when a directory matches the HOME directory. This option is ignored when which is invoked as root. --tty-only Stop processing options on the right if not on tty. --version,-v,-V Print version information on standard output then exit successfully. --help Print usage information on standard output then exit successfully. RETURN VALUE
Which returns the number of failed arguments, or -1 when no `programname' was given. EXAMPLE
The recommended way to use this utility is by adding an alias (C shell) or shell function (Bourne shell) for which like the following: [ba]sh: which () { (alias; declare -f) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot $@ } export -f which [t]csh: alias which 'alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde' This will print the readable ~/ and ./ when starting which from your prompt, while still printing the full path when used from a script: > which q2 ~/bin/q2 > echo `which q2` /home/carlo/bin/q2 BUGS
The HOME directory is determined by looking for the HOME environment variable, which aborts when this variable doesn't exist. Which will consider two equivalent directories to be different when one of them contains a path with a symbolic link. AUTHOR
Carlo Wood <carlo@gnu.org> SEE ALSO
bash(1) WHICH(1)
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