Assign user input to already declared array Post: 302553468

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Top Forums Shell Programming and Scripting Assign user input to already declared array Post 302553468 by Corona688 on Wednesday 7th of September 2011 05:05:36 PM

09-07-2011

Registered User

BASH is a string language with weak types, so copying an entire array around like that means having to handle it as a string.

There is an operator to turn an array into one string: "${ARR[*]}" But how're you going to do that when all you have is the name of the array, not the array itself? "${!ARR[*]}" doesn't work, the precedence is wrong, and you can't put the[*] outside it to do it backwards. You could shove it all into an eval, which can accomplish any weird syntax you want, but would be difficult. And then you have to turn it back into an array, wrapping it in another layer of stuff.

It's easy to turn a string into an array, though, and BASH has the ! operator to turn a variable name into a variable string. So why not keep your data as strings for easy retrieval?

Code:

#!/bin/bash

# Not arrays -- just strings.  Split them later.
colors="red blue yellow"
red="cherry fire"
blue="baby sky"
yellow="canary banana"

# This variable is used to read other variables.
name="colors"

while [ ! -z "${!name}" ]
do
        # Fill an array with variable name stored in 'name'.
        # i.e. When it's 'colors', it gets filled with ( red blue yellow )
        ARR=( ${!name} )
        echo "Choose a color counting from 0: ${ARR[*]}"
        read choice
        name="${ARR[$choice]}"
done

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scandir

scandir(3)						     Library Functions Manual							scandir(3)

Name
       scandir - scan a directory

Syntax
       #include <sys/types.h>
       #include <sys/dir.h>

       scandir(dirname, namelist, select, compar)
       char *dirname;
       struct direct *(*namelist[]);
       int (*select)();
       int (*compar)();

       alphasort(d1, d2)
       struct direct **d1, **d2;

Description
       The  subroutine	reads the directory dirname and builds an array of pointers to directory entries using It returns the number of entries in
       the array and a pointer to the array through namelist.

       The select parameter is a pointer to a user supplied subroutine which is called by to select which entries are to be included in the array.
       The  select routine is passed a pointer to a directory entry and should return a non-zero value if the directory entry is to be included in
       the array.  If select is null, then all the directory entries will be included.

       The compar parameter is a pointer to a user supplied subroutine which is passed to to sort the completed array.	If this pointer  is  null,
       the array is not sorted.  The is a routine which can be used for the compar parameter to sort the array alphabetically.

       The  memory  allocated  for  the array can be deallocated with free by freeing each pointer in the array and the array itself.  For further
       information, see

Diagnostics
       Returns -1 if the directory cannot be opened for reading or if cannot allocate enough memory to hold all the data structures.

See Also
       directory(3), malloc(3), qsort(3), dir(5)

																	scandir(3)

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