System command as variable in C - c

Question

I would like to get which command as a parameter of execv. For example user types "firefox" as an input. It will show the file path with which firefox command and i would like to use it in execv.
Here is my try :
int main(void)
{
//char inputBuffer[MAX_LINE]; /*buffer to hold command entered */
char *args[MAX_LINE/2 + 1]; /*command line arguments */
while (1){
char command1[50] = "which ";
char *input = args[0]; /* args[0] holds input */
strcat(command1,input);
char *const parmList[] = {input,NULL};
char buf[100]; /* will convert command to the file path */
char *str;
FILE *file;
if (NULL == (file = popen(command1, "r"))) {
perror("popen");
exit(EXIT_FAILURE);
}
while (fgets(buf, sizeof(buf), file) != NULL) {
}
pclose(file);
int count=0;
for(int m=0;m<buf[m];m++){
if(buf[m] != ' ')
count++;
}
char x5[count];
for(int t=0;t<=count;t++){
x5[t]=buf[t];
}
printf("%s\n\n\n\n",x5); /*i tried to delete spaces from 'buf'
but there is something wrong in file path the output is something like that :
(input : firefox)
usr/bin/firefox
(some weird characters)
because of weird characters execv don't get filepath correctly. I have to this
only with execv
*/
pid_t childpid;
childpid = fork();
if (childpid == -1) {
printf("error");
}
if (childpid == 0) {
execv(x5, parmList);
}
}
}

Answer 1

there are, as you noticed, a few problems with the two loops that are trying to remove any embedded spaces in the value being passed as first param to execv()
Note: always place the literal on the left to have compiler catch error if accidentally wrote an assignment rather than a comparison statement.
1) failed to trim any trailing newline from the buf[] array.
2) those loops are, well, not correct. Suggest:
// remove trailing newline
char * newline = NULL;
if( NULL != (newline = strstr( buf, "\n") ) )
{ // then trim newline
*newline = '\0';
}
// data declarations for removing space characters
char *sourceIndex = buf;
char *targetIndex = buf;
// following loop removes space characters, in place
// and stops when the string terminator char encountered
for( ; sourceIndex; sourceIndex++)
{
if( ' ' != *sourceIndex )
{ // then char to have in final output
*targetIndex = *sourceIndex; // copy it
targetIndex++; // step to next position in target
}
}
*targetIndex = '\0'; // terminate the (possibly shorter) string
...
// pass to new process
if( 0 == childpid )
{ // then child process
execv(buf, parmList); // only returns if execv() failed
perror( "execv failed" );
exit( EXIT_FAILURE );
}