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// makeCWrapper /path/to/executable \
--argv0 my-wrapper \
--set-default MESSAGE HELLO \
--prefix PATH : /usr/bin/ \
--suffix PATH : /usr/local/bin/ \
--add-flags "-x -y -z" \
--set MESSAGE2 WORLD
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <stdio.h>
#define assert_success(e) do { if ((e) < 0) { perror(#e); abort(); } } while (0)
char *concat3(char *x, char *y, char *z) {
int xn = strlen(x);
int yn = strlen(y);
int zn = strlen(z);
char *res = malloc(sizeof(*res)*(xn + yn + zn + 1));
assert(res != NULL);
strncpy(res, x, xn);
strncpy(res + xn, y, yn);
strncpy(res + xn + yn, z, zn);
res[xn + yn + zn] = '\0';
return res;
}
void set_env_prefix(char *env, char *sep, char *val) {
char *existing = getenv(env);
if (existing) val = concat3(val, sep, existing);
assert_success(setenv(env, val, 1));
if (existing) free(val);
}
void set_env_suffix(char *env, char *sep, char *val) {
char *existing = getenv(env);
if (existing) val = concat3(existing, sep, val);
assert_success(setenv(env, val, 1));
if (existing) free(val);
}
int main(int argc, char **argv) {
assert_success(setenv("MESSAGE", "HELLO", 0));
set_env_prefix("PATH", ":", "/usr/bin/");
set_env_suffix("PATH", ":", "/usr/local/bin/");
putenv("MESSAGE2=WORLD");
char **argv_tmp = calloc(4 + argc, sizeof(*argv_tmp));
assert(argv_tmp != NULL);
argv_tmp[0] = argv[0];
argv_tmp[1] = "-x";
argv_tmp[2] = "-y";
argv_tmp[3] = "-z";
for (int i = 1; i < argc; ++i) {
argv_tmp[3 + i] = argv[i];
}
argv_tmp[3 + argc] = NULL;
argv = argv_tmp;
argv[0] = "my-wrapper";
return execv("/path/to/executable", argv);
}
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