Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
#+ declared and set within the function.
}
original_array=( element1 element2 element3 element4 element5 )
echo
echo "original_array = ${original_array[@]}"
# List all elements of original array.
# This is the trick that permits passing an array to a function.
# **********************************
argument=`echo ${original_array[@]}`
# **********************************
# Pack a variable
#+ with all the space−separated elements of the original array.
#
# Note that attempting to just pass the array itself will not work.
# This is the trick that allows grabbing an array as a "return value".
# *****************************************
returned_array=( `Pass_Array "$argument"` )
# *****************************************
# Assign 'echoed' output of function to array variable.
echo "returned_array = ${returned_array[@]}"
echo "============================================================="
# Now, try it again,
#+ attempting to access (list) the array from outside the function.
Pass_Array "$argument"
# The function itself lists the array, but...
#+ accessing the array from outside the function is forbidden.
echo "Passed array (within function) = ${passed_array[@]}"
# NULL VALUE since this is a variable local to the function.
echo
exit 0
For a more elaborate example of passing arrays to functions, see Example A−11.
• Using the double parentheses construct, it is possible to use C−like syntax for setting and
incrementing variables and in for and while loops. See Example 10−12 and Example 10−17.
• A useful scripting technique is to repeatedly feed the output of a filter (by piping) back to the same
filter, but with a different set of arguments and/or options. Especially suitable for this are tr and grep.
# From "wstrings.sh" example.
wlist=`strings "$1" | tr A−Z a−z | tr '[:space:]' Z | \
tr −cs '[:alpha:]' Z | tr −s '\173−\377' Z | tr Z ' '`
Example 34−13. Fun with anagrams
#!/bin/bash
Chapter 34. Miscellany 352