How to replace a multi-character character constant with one character [closed] - c

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I'm attempting to replace '%7C' with a '|' in C but i'm getting a multi-character character constant warning. I was wondering if it was possible to do this and if so how? I was attempting using the code below but it gave this warning.
Parse.c
char *parse(char *command){
char * newCommand = (char *)malloc(sizeof(char)*35);
newCommand = strtok(command, " ");
newCommand = strtok(NULL, "/run?command= ");
for(int i = 0; i<strlen(newCommand); i++){
if(newCommand[i] == '+')
{
newCommand[i] = ' ';
}
if(newCommand[i] == '%7C')
{
newCommand[i] = '|';
}
}
return newCommand;
}

Answer 1

Multi-character constants are not portable and should generally be avoided. Your code comes under the 'general' category.
Part of the solution to your problem is to do a string comparison (with strncmp):
if (strncmp(&newCommand[i], "%7C", 3) == 0)
{
newCommand[i] = '|';
}
However, you also need to remove the 7C. That requires more surgery on the loop:
int tgt = 0;
int len = strlen(newCommand);
for (int src = 0; src < len; src++)
{
if (newCommand[src] == '+')
{
newCommand[tgt++] = ' ';
}
else if (strncmp(newCommand[i], "%7C", 3) == 0)
{
newCommand[tgt++] = '|';
src += 2;
}
else
newCommand[tgt++] = newCommand[src];
}
newCommand[tgt] = '\0';
This maintains two indexes into the newCommand array, one from which you're reading (src) and one to which you're writing (tgt — dst would be an alternative name). The src += 2; skips over the 7C after replacing % with |.
Uncompiled code!
Also, in your function you have:
char *newCommand = (char *)malloc(sizeof(char)*35);
newCommand = strtok(command, " ");
This immediately leaks the allocated memory. Maybe you need to use strdup() or:
char *newCommand = malloc(strlen(command) + 1);
if (newCommand == NULL) …report error and bail out…
strcpy(newCommand, command);
And the next line:
newCommand = strtok(NULL, "/run?command= ");
splits on any sequence of any of the characters in the constant string; it does not look for that string. If you want to look for the string, then you need strstr() instead, and you need to run strtok() first, perhaps, to get the right starting point (maybe newCommand = strtok(NULL, ""), then char *end = strstr(newCommand, "/run?command= "); — and check for null pointers returned.
With the revised allocation, you need a new symbol to record the pointers returned by strtok() — such as char *token;.
All in all, there's a lot of work needed on your code.