VERBOSE environment in shell script - bash

Question

I'm trying to write a Bash script, which compiles and runs all C files in the current directory. My Bash script is the following:
#!/bin/bash
LIST="$(ls *.c)"
echo "Compile all C source files"
for f in $( ls *.c); do
#echo "C file: $f"
gcc $f -o "${f%.*}"
./"${f%.*}"
done
Now, I'm trying to define a VERBOSE environment variable. If VERBOSE environment variable is set then my Bash script should display the command that is being used to compile the source file.
How can I define such a VERBOSE environment variable in this Bash script?
When verbose is defined my output should be like,
Compiling all C source files:
gcc copyfile.c -o copyfile
---- successful ----
gcc haserror.c -o haserror
haserror.c: In function ‘main’:
haserror.c:9:10: warning: missing terminating " character
printf("Hello !\n);
^
haserror.c:9:10: error: missing terminating " character
printf("Hello!\n);
^~~~~~~~~~~~~~~~~~~
haserror.c:11:1: error: expected expression before ‘}’ token
}
^
haserror.c:11:1: error: expected ‘;’ before ‘}’ token
gcc hello.c -o hello
---- successful ----
gcc p005.c -o p002
---- successful ----
gcc p103.c -o p101
---- successful ----
gcc p102.c -o p105
---- successful ----
============
5 C source files are compiled successfully.
1 C source files have compilation error(s).
**Otherwise, when my VERBOSE not defined, my output should be like**
Compiling all C source files:
haserror.c: In function ‘main’:
haserror.c:9:10: warning: missing terminating " character
printf("Hello!\n);
^
haserror.c:9:10: error: missing terminating " character
printf("Hello!\n);
^~~~~~~~~~~~~~~~~~~
haserror.c:11:1: error: expected expression before ‘}’ token
}
^
haserror.c:11:1: error: expected ‘;’ before ‘}’ token
============
5 C source files are compiled successfully.
1 C source files have compilation error(s).

Answer 1

The trivially obvious shoud work.
#!/bin/bash
[ "$VERBOSE" ] && echo "$0: Compile all C source files" >&2
for f in *.c; do
[ "$VERBOSE" ] && echo "$0: C file: $f" >&2
# [ "$VERBOSE" ] && set -x
gcc $f -o "${f%.*}"
# set +x
./"${f%.*}"
done
Notice also how we avoid the useless (and slightly dangerous) use of ls and print the diagnostic output to standard error, with the script's name included in the message.
The condition is simple; [ "$VERBOSE" ] evaluates to true (returns a zero exit code) when VERBOSE is set and non-empty. You can perform arbitrarily complex actions conditionally using the shell's normal flow control statements, such as perhaps
if [ "$VERBOSE" ]; then
echo "$0: compiling $f" >&2
(set -x; gcc "$f" -o "${f.c}") &&
echo "$0: ----- $f: successful -----" >&2
else
gcc "$f" -o "${f.c}"
fi
(though I would perhaps then also refactor the compilation command into a separate function.)
A better design is to have the script accept a command-line option. Also, you should probably avoid using upper case for your private variables.