OK, so basically I would like getopt_long to only modify a flag variable if the user supplied a command-line option to do so. Otherwise, I want the flag left alone. I've found a solution for this, but it's not very beautiful. In particular, if there are lots of flags, then this gets pretty verbose. Is there a better way?:
#include <getopt.h>
#include <stdlib.h>
#include <stdio.h>
// I would like this function to only override myflag and myvariable if the user supplies them.
int parse_commandLineOptions(int argc, char *argv[], int *pointer_myflag){
// Non-flag parameters "need" to be static or global to be accessible to getopt_long()
static int set_myflag, unset_myflag;
static struct option longopts[] = {
// This is what I'd really like to do, but it's not permitted because myflag isn't static.
// Do you haz teh codez?
//{"set", no_argument, pointer_myflag, true},
//{"unset", no_argument, pointer_myflag, false}
// Instead this is the best I've come up with.
{"set", no_argument, &set_myflag, 1},
{"unset", no_argument, &unset_myflag, 1}
};
// This normally wouldn't be empty.
char shortopts[] = "";
int curChar=0;
while(curChar!=-1){
// Get the character representing the current command-line argument
int option_index=0;
curChar=getopt_long(argc, argv, shortopts, longopts, &option_index);
if(curChar== -1)
break;
switch(curChar){
// The user supplied one of the flag-setting options.
case 0:
break;
// Normally I would parse non-flag parameters here.
//case 'x':
// do something.
// getopt_long will itself print an error message in this case.
case '?':
fprintf(stderr, "# Usage: not what you did.\n");
exit(1);
// This should never happen.
default:
fprintf(stderr, "# Error: Could not parse curChar in parse_commandLineOptions().\n");
exit(1);
} // Closes switch(curChar)
} // Closes while(curChar!=-1)
// Normally I would parse non-argument parameters here.
// :(
if(set_myflag) *pointer_myflag=1;
else if(unset_myflag) *pointer_myflag=0;
return 0;
}
int main(int argc, char *argv[]){
// If the user supplies --set, myflag will be 1
// If the user supplies --unset, myflag will be 0
// If the user doesn't supply anything, myflag will be left as is.
int myflag=1337;
parse_commandLineOptions(argc, argv, &myflag);
printf("myflag = %d\n", myflag);
}
All I had to do was lose the static keyword on longopts!
#include <getopt.h>
#include <stdlib.h>
#include <stdio.h>
// This function only overrides myflag and myvariable if the user supplies them.
int parse_commandLineOptions(int argc, char *argv[], int *pointer_myflag){
// ALL YOUR BASE ARE BELONG TO US!
struct option longopts[] = {
{"set", no_argument, pointer_myflag, 1},
{"unset", no_argument, pointer_myflag, 0}
};
// This normally wouldn't be empty.
char shortopts[] = "";
int curChar=0;
while(curChar!=-1){
// Get the character representing the current command-line argument
int option_index=0;
curChar=getopt_long(argc, argv, shortopts, longopts, &option_index);
if(curChar== -1)
break;
switch(curChar){
// The user supplied one of the flag-setting options.
case 0:
break;
// Normally I would parse non-flag parameters here.
//case 'x':
// do something.
// getopt_long will itself print an error message in this case.
case '?':
fprintf(stderr, "# Usage: not what you did.\n");
exit(1);
// This should never happen.
default:
fprintf(stderr, "# Error: Could not parse curChar in parse_commandLineOptions().\n");
exit(1);
} // Closes switch(curChar)
} // Closes while(curChar!=-1)
// Normally I would parse non-argument parameters here.
// :)
return 0;
}
int main(int argc, char *argv[]){
// If the user supplies --set, myflag will be 1
// If the user supplies --unset, myflag will be 0
// If the user doesn't supply anything, myflag will be left as is.
int myflag=1337;
parse_commandLineOptions(argc, argv, &myflag);
printf("myflag = %d\n", myflag);
}