I found myself in the middle of a rather large Bash project a little while back. Basically, I had defined several file paths in variable names and needed to access that information dynamically.
The scenario is this: a value would be supplied by the user, and I had to pull out some hard-wired information based on this value. So, suppose you were writting a script that referenced file types arranged by extenstions and was selected by the user at run time. This would be easily solvable in the following:
#!/usr/bin/env bash
# List of variables maybe in some other file
JPG_FILE_PATH="/opt/path/one"
DOC_FILE_PATH="/opt/path/two"
MP3_FILE_PATH="/opt/path/three"
XLS_FILE_PATH="/opt/path/four"
get_file_path() {
local ID=${1-''}
# Sets FILE_PATH to the desired value. If not exist then null.
FILE_PATH=$(eval "echo \${$(echo ${ID}_FILE_PATH)"-''})
}
get_file_path "MP3"
echo $FILE_PATH
$ ./test_pre.sh
/opt/path/three
The above snippet -- admittedly a bit humorous -- is very useful in several situations. I happened to use it in creating a shell library of functions and paths that are used by others in the easy creation of scripts around Oracle RDBMS.
