STRTOL(3) BSD Programmer's Manual STRTOL(3)
strtol, strtoll, strtoq - convert string value to a long or long long in- teger
#include <stdlib.h> #include <limits.h> long strtol(const char *nptr, char **endptr, int base); #include <stdlib.h> #include <limits.h> long long strtoll(const char *nptr, char **endptr, int base); #include <sys/types.h> #include <stdlib.h> #include <limits.h> quad_t strtoq(const char *nptr, char **endptr, int base);
The strtol() function converts the string in nptr to a long value. The strtoll() function converts the string in nptr to a long long value. The strtoq() function is a deprecated equivalent of strtoll() and is provided for backwards compatibility with legacy programs. The conversion is done according to the given base, which must be a number between 2 and 36 in- clusive or the special value 0. The string may begin with an arbitrary amount of whitespace (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-null, 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.)
The strtol() function returns the result of the conversion, unless the value would underflow or overflow. If an underflow occurs, strtol() re- turns LONG_MIN. If an overflow occurs, strtol() returns LONG_MAX. In both cases, errno is set to ERANGE. The strtoll() function has identical return values except that LLONG_MIN and LLONG_MAX are used to indicate underflow and overflow respectively.
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 re- turn 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' || *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 trailing whi- tespace is acceptable, further checks must be done on *ep; alternately, 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' || *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;
[ERANGE] The given string was out of range; the value converted has been clamped.
atof(3), atoi(3), atol(3), atoll(3), sscanf(3), strtod(3), strtoul(3)
The strtol() and strtoll() functions conform to ISO/IEC 9899:1999 ("ISO C99"). The strtoq() function is a BSD extension and is provided for back- wards compatibility with legacy programs.
Ignores the current locale. MirOS BSD #10-current June 25, 1992 1
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