How can I compare strings in C using a `switch` statement?

If you mean, how to write something similar to this:

// switch statementswitch (string) {  case "B1":     // do something    break;  /* more case "xxx" parts */}

Then the canonical solution in C is to use an if-else ladder:

if (strcmp(string, "B1") == 0) {  // do something} else if (strcmp(string, "xxx") == 0){  // do something else}/* more else if clauses */else /* default: */{}

If you have many cases and do not want to write a ton of strcmp() calls, you could do something like:

switch(my_hash_function(the_string)) {    case HASH_B1: ...    /* ...etc... */}

You just have to make sure your hash function has no collisions inside the set of possible values for the string.

There is no way to do this in C. There are a lot of different approaches. Typically the simplest is to define a set of constants that represent your strings and do a look up by string on to get the constant:

#define BADKEY -1#define A1 1#define A2 2#define B1 3#define B2 4typedef struct { char *key; int val; } t_symstruct;static t_symstruct lookuptable[] = {    { "A1", A1 }, { "A2", A2 }, { "B1", B1 }, { "B2", B2 }};#define NKEYS (sizeof(lookuptable)/sizeof(t_symstruct))int keyfromstring(char *key){    int i;    for (i=0; i < NKEYS; i++) {        t_symstruct *sym = lookuptable[i];        if (strcmp(sym->key, key) == 0)            return sym->val;    }    return BADKEY;}/* ... */switch (keyfromstring(somestring)) {case A1: /* ... */ break;case A2: /* ... */ break;case B1: /* ... */ break;case B2: /* ... */ break;case BADKEY: /* handle failed lookup */}

There are, of course, more efficient ways to do this. If you keep your keys sorted, you can use a binary search. You could use a hashtable too. These things change your performance at the expense of maintenance.