find the length of a formatted string in C

Question

I have below function in my application:

 void func(char *file, int line)
 {
    char stmt[150];
    sprintf(stmt, "Failed in file %s, at line number %d", file, line);
 }

Here I am taking char array of 150 bytes(rough guess), instead I need to find the length of the string that I gave in sprintf() and take the array of that size.

Pls suggest me if such facility in C to find the length of a formatted string. Thanks !

If you do not have an upper bound for the length of `file`, you need to allocate the necessary amount of memory by using `malloc()`. — Erich Kitzmueller, Nov 13 '14 at 13:58
`int length = snprintf(NULL, 0, "Failed in file %s, at line number %d", file, line);` — BLUEPIXY, Nov 13 '14 at 13:59
Related: http://stackoverflow.com/questions/3774417/sprintf-with-automatic-memory-allocation — abligh, Nov 13 '14 at 19:36

score 7 · Accepted Answer · answered Nov 13 '14 at 14:00

7

What about snprintf? The function does not write more characters than given number, but returns the length of the string it would create if it had enough space.

 int len = snprintf(NULL, 0, "Failed in file %s, at line number %d", file, line);

answered Nov 13 '14 at 14:00

Lubomír Sedlář

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find the length of a formatted string in C

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