C - Concat Strings

c, char, concatenation, string

Solution

Your `getMonth` returns a pointer to a string literal. Attempting to modify it(e.g., with `strcat`) isn't allowed -- it leads to undefined behavior.

I'd (strongly) suggest using `strftime` to handle formatting date and/or time strings for printing. This will not only reduce your formatting code to a one-liner, but also let you support localized results when/if you want as well.

Edit: if you can't use `strftime`, you'll want to build a formatted date in your own buffer, probably using `sprintf`:

char buffer[256];
static const char *months[] = {
    "January", 
    "February", 
    /* ... */ , 
    "November", 
    "December"
};

sprintf(buffer, "%s %d %d", months[monthnum], day, year);

Problem

Trying to concat strings (*char) using C and having a lot of segmentation faults: ``` void printDateFormat( char *in ) { /* begin function printDateFormat */ char *month; // month by char int month_int; // month by digit char *day; // day by char char *year; // year by char char *dateToken; // date token in split char *formatted; // formatted string dateToken = strtok (in, "/"); month = &dateToken; formatted = formatted = getMonth(month); dateToken = strtok (NULL, "/"); day = &dateToken; formatted = strcat (formatted, day); formatted = strcat (formatted, ", "); dateToken = strtok (NULL, "/"); year = &dateToken; formatted = strcat (formatted, year); in = *formatted; } /* End function printDateFormat */ char *getMonth( int d) { /* begin function *getMonth */ switch (d) { case 1: return "January"; // break; case 2: return "February"; // break; case 3: return "March"; // break; case 4: return "April"; // break; case 5: return "May"; // break; case 6: return "June"; // break; case 7: return "July"; // break; case 8: return "August"; // break; case 9: return "September"; // break; case 10: return "October"; // break; case 11: return "November"; // break; case 12: return "December"; // break; } } /* End function *getMonth */ ``` Input into printDateFormat() is expected as another string in the format: MM/dd/yyyy ... ie. 03/31/2013. Purpose is to turn that into: March 31, 2013. EDIT: Here's how I pass into `printDateFormat` ``` void option1( void ) { /* begin function option1 */ char date[10]; /*user input date string */ printf("\n\nEnter date [Format: MM/dd/yyyy]: "); fgets(date, 10, stdin); scanf("%s", &date); printDateFormat(date); printf("\n%s", date); } /* End function option2 */ ``` EDIT 2: Ok, made a few changes but still no dice... here's my compiler warning: ``` asgn9.c: In function `printDateFormat': asgn9.c:224: warning: passing arg 1 of `getMonth' makes integer from pointer without a cast asgn9.c:237: warning: assignment makes pointer from integer without a cast ``` they refer to the use of `getMonth()` within my `printDateFormat()` Here's my updated code, I still get a segmentation fault at the same spot... ``` void printDateFormat( char *in ) { /* begin function printDateFormat */ char *month; // month by char int month_int; // month by digit char *day; // day by char char *year; // year by char char *dateTkn; // date token in split char *formatted; // formatted string dateTkn = strtok (in, "/"); month = dateTkn; formatted = getMonth(month); dateTkn = strtok (NULL, "/"); day = dateTkn; formatted = strcat (formatted, day); formatted = strcat (formatted, ", "); dateTkn = strtok (NULL, "/"); year = dateTkn; formatted = strcat (formatted, year); in = *formatted; } /* End function printDateFormat */ char *getMonth( int d) { /* begin function *getMonth */ static char *months[] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"}; return strcpy(malloc(32), months[d]); } /* End function *getMonth */ ```

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