strtol(3C)

NAME

strtol(), atol(), atoi(), strtoul(), strtoll(), strtoull() — convert string to integer

SYNOPSIS

#include <stdlib.h>

long strtol(const char *str, char **ptr, int base);

long long strtoll(const char *str, char **ptr, int base);

long atol(const char *str);

int atoi(const char *str);

unsigned long strtoul(const char *str, char **ptr, int base);

unsigned long long strtoull(const char *str, char **ptr, int base);

DESCRIPTION

strtol() or strtoul() converts the character string pointed to by str to long int or unsigned long int representation, respectively. strtoll() or strtoull() converts the character string pointed to by str to long long or unsigned long long representation, respectively. The string is scanned up to the first character inconsistent with the base. Leading ``white-space'' characters (as defined by isspace() in ctype(3C)) are ignored. If no conversion can take place, zero is returned.

If base is greater than or equal to 2 and less than or equal to 36, it is used as the base for conversion. After an optional leading sign, leading zeros are ignored, and 0x or 0X is ignored if base is 16.

If base is zero, the string itself determines the base as follows: after an optional leading sign, a leading zero indicates octal conversion; a leading 0x or 0X indicates hexadecimal conversion. Otherwise, decimal conversion is used.

If the value of ptr is not (char **)NULL, a pointer to the character terminating the scan is returned in the location pointed to by ptr. If no integer can be formed, the location pointed to by ptr is set to str, and zero is returned.

atol(str) is equivalent to strtol(str, (char **)NULL, 10).

atoi(str) is equivalent to int strtol(str, (char **)NULL, 10).

RETURN VALUE

Upon successful completion, all functions return the converted value, if any.

If the correct value would cause overflow:

strtol(): returns LONG_MAX or LONG_MIN (according to the sign of the value), and sets errno to ERANGE;
strtoul(): returns ULONG_MAX and sets errno to ERANGE.
strtoll(): returns LONG_LONG_MAX or LONG_LONG_MIN (according to the sign of the value), and sets errno to ERANGE;
strtoull(): returns ULONG_LONG_MAX and sets errno to ERANGE.

Overflow conditions are ignored by atol() and atoi().

For all other errors, zero is returned and errno is set to indicate the error.

ERRORS

strtol(), strtoul(), strtoll() and strtoull() fail and errno is set, if any of the following conditions are encountered:

EINVAL: The value of base is not supported.
ERANGE: The value to be returned would have caused overflow.

AUTHOR

These interfaces were developed by OSF and HP.

STANDARDS CONFORMANCE

strtol(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, ANSI C

atoi(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C

atol(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C

strtoul(): AES, SVID3, XPG4, ANSI C

strtoll(): C99

strtoull(): C99

strtol(3C)

Technical documentation

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