strtol(3) - NetBSD Manual Pages

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STRTOL(3)               NetBSD Library Functions Manual              STRTOL(3)


NAME
strtol, strtoll, strtoimax, strtoq -- convert string value to a long, long long, intmax_t or quad_t integer
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdlib.h> #include <limits.h> long int strtol(const char * restrict nptr, char ** restrict endptr, int base); long long int strtoll(const char * restrict nptr, char ** restrict endptr, int base); #include <inttypes.h> intmax_t strtoimax(const char * restrict nptr, char ** restrict endptr, int base); #include <sys/types.h> #include <stdlib.h> #include <limits.h> quad_t strtoq(const char * restrict nptr, char ** restrict endptr, int base);
DESCRIPTION
The strtol() function converts the string in nptr to a long int value. The strtoll() function converts the string in nptr to a long long int value. The strtoimax() function converts the string in nptr to an intmax_t value. The strtoq() function converts the string in nptr to a quad_t value. The conversion is done according to the given base, which must be between 2 and 36 inclusive, or be the special value 0. The string may begin with an arbitrary amount of white space (as deter- mined by isspace(3)) followed by a single optional `+' or `-' 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 `0', in which case it is taken as 8 (octal). The remainder of the string is converted to a long 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 `A' in either upper or lower case represents 10, `B' represents 11, and so forth, with `Z' represent- ing 35.) If endptr is non nil, strtol() stores the address of the first invalid character in *endptr. If there were no digits at all, however, strtol() stores the original value of nptr in *endptr. (Thus, if *nptr is not `\0' but **endptr is `\0' on return, the entire string was valid.)
RETURN VALUES
The strtol() function returns the result of the conversion, unless the value would underflow or overflow. If an underflow occurs, strtol() returns LONG_MIN, strtoll() returns LLONG_MIN, and strtoimax() returns INTMAX_MIN. If an overflow occurs, strtol() returns LONG_MAX, strtoll() returns LLONG_MAX, and strtoimax() returns INTMAX_MAX. In these cases, errno is set to ERANGE.
EXAMPLES
Ensuring that a string is a valid number (i.e., in range and containing no trailing characters) requires clearing errno beforehand explicitly since errno is not changed on a successful call to strtol(), and the return value of strtol() cannot be used unambiguously to signal an error: char *ep; long lval; ... errno = 0; lval = strtol(buf, &ep, 10); if (buf[0] == '\0' || *ep != '\0') goto not_a_number; if (errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN)) goto out_of_range; This example will accept ``12'' but not ``12foo'' or ``12\n''. If trail- ing whitespace is acceptable, further checks must be done on *ep; alter- nately, use sscanf(3). If strtol() is being used instead of atoi(3), error checking is further complicated because the desired return value is an int rather than a long; however, on some architectures integers and long integers are the same size. Thus the following is necessary: char *ep; int ival; long lval; ... errno = 0; lval = strtol(buf, &ep, 10); if (buf[0] == '\0' || *ep != '\0') goto not_a_number; if ((errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN)) || (lval > INT_MAX || lval < INT_MIN)) goto out_of_range; ival = lval;
ERRORS
[ERANGE] The given string was out of range; the value converted has been clamped.
SEE ALSO
atof(3), atoi(3), atol(3), atoll(3), strtod(3), strtoul(3), strtoull(3), strtoumax(3)
STANDARDS
The strtol() function conforms to ANSI X3.159-1989 (``ANSI C89''). The strtoll() and strtoimax() functions conform to ISO/IEC 9899:1999 (``ISO C99'').
BUGS
Ignores the current locale. NetBSD 5.0 August 11, 2002 NetBSD 5.0
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