STRTOL

NAME

SYNOPSIS

#include <stdlib.h>

long int strtol(const char *nptr, char **endptr, int base);

long long int strtoll(const char *nptr, char **endptr, int base);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

strtoll(): XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE || _ISOC99_SOURCE; or cc -std=c99  

DESCRIPTION

The string may begin with an arbitrary amount of white space (as determined by isspace(3)) followed by a single optional aq+aq or aq-aq sign. If base is zero or 16, the string may then include a "0x" prefix, and the number will be read in base 16; otherwise, a zero base is taken as 10 (decimal) unless the next character is aq0aq, in which case it is taken as 8 (octal).

The remainder of the string is converted to a long int value in the obvious manner, stopping at the first character which is not a valid digit in the given base. (In bases above 10, the letter aqAaq in either upper or lower case represents 10, aqBaq represents 11, and so forth, with aqZaq representing 35.)

If endptr is not NULL, strtol() stores the address of the first invalid character in *endptr. If there were no digits at all, strtol() stores the original value of nptr in *endptr (and returns 0). In particular, if *nptr is not aq\0aq but **endptr is aq\0aq on return, the entire string is valid.

The strtoll() function works just like the strtol() function but returns a long long integer value.  

RETURN VALUE

ERRORS

EINVAL

(not in C99) The given base contains an unsupported value.

ERANGE

The resulting value was out of range.

The implementation may also set errno to EINVAL in case no conversion was performed (no digits seen, and 0 returned).  

CONFORMING TO

NOTES

In locales other than the "C" locale, other strings may also be accepted. (For example, the thousands separator of the current locale may be supported.)

BSD also has

quad_t strtoq(const char *nptr, char **endptr, int base);

EXAMPLE

$ ./a.out 123
strtol() returned 123
$ ./a.out aq    123aq
strtol() returned 123
$ ./a.out 123abc
strtol() returned 123
Further characters after number: abc
$ ./a.out 123abc 55
strtol: Invalid argument
$ ./a.out aqaq
No digits were found
$ ./a.out 4000000000
strtol: Numerical result out of range

Program source

#include <stdlib.h>
#include <limits.h>
#include <stdio.h>
#include <errno.h>

int
main(int argc, char *argv[])
{
    int base;
    char *endptr, *str;
    long val;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s str [base]\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    str = argv[1];
    base = (argc > 2) ? atoi(argv[2]) : 10;

    errno = 0;    /* To distinguish success/failure after call */
    val = strtol(str, &endptr, base);

    /* Check for various possible errors */

    if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
            || (errno != 0 && val == 0)) {
        perror("strtol");
        exit(EXIT_FAILURE);
    }

    if (endptr == str) {
        fprintf(stderr, "No digits were found\n");
        exit(EXIT_FAILURE);
    }

    /* If we got here, strtol() successfully parsed a number */

    printf("strtol() returned %ld\n", val);

    if (*endptr != aq\0aq)        /* Not necessarily an error... */
        printf("Further characters after number: %s\n", endptr);

    exit(EXIT_SUCCESS);
}

SEE ALSO

COLOPHON