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from: @(#)strtol.3 8.1 (Berkeley) 6/4/93
.Dd December 27, 2014 .Dt STRTOL 3 .Os .Sh NAME .Nm strtoi , .Nm strtol , .Nm strtoll , .Nm strtoimax , .Nm strtoq .Nd convert string value to a long, long long, intmax_t or quad_t integer .Sh LIBRARY .Lb libc .Sh SYNOPSIS n stdlib.h n limits.h .Ft long int .Fn strtol "const char * restrict nptr" "char ** restrict endptr" "int base" .Ft long long int .Fn strtoll "const char * restrict nptr" "char ** restrict endptr" "int base"
p n inttypes.h .Ft intmax_t .Fn strtoi "const char * restrict nptr" "char ** restrict endptr" "int base" "intmax_t lo" "intmax_t hi" "int *rerror" .Ft intmax_t .Fn strtoimax "const char * restrict nptr" "char ** restrict endptr" "int base"
p n sys/types.h n stdlib.h n limits.h .Ft quad_t .Fn strtoq "const char * restrict nptr" "char ** restrict endptr" "int base" .Sh DESCRIPTION The .Fn strtol function converts the string in .Fa nptr to a .Ft long int value. The .Fn strtoll function converts the string in .Fa nptr to a .Ft long long int value. The .Fn strtoimax function converts the string in .Fa nptr to an .Ft intmax_t value. The .Fn strtoi function is using internally .Fn strtoimax and ensures that the result is always in the range [ .Fa lo .. .Fa hi ]. In adddition it always places .Dv 0 on success or an error value in the .Fa rerror argument, avoiding the .Dv errno gymnastics the other functions require. The .Fa rerror argument can be .Dv NULL if errors are to be ignored. The .Fn strtoq function converts the string in .Fa nptr to a .Ft quad_t value. The conversion is done according to the given .Fa base , which must be between 2 and 36 inclusive, or be the special value 0.
p The string may begin with an arbitrary amount of white space (as determined by .Xr isspace 3 ) followed by a single optional .Ql + or .Ql - sign. If .Fa base is zero or 16, the string may then include a .Ql 0x prefix, and the number will be read in base 16; otherwise, a zero .Fa base is taken as 10 (decimal) unless the next character is .Ql 0 , in which case it is taken as 8 (octal).
p The remainder of the string is converted to a .Em 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 .Ql A in either upper or lower case represents 10, .Ql B represents 11, and so forth, with .Ql Z representing 35.)
p If .Fa endptr is non-nil, .Fn strtol stores the address of the first invalid character in .Fa *endptr . If there were no digits at all, however, .Fn strtol stores the original value of .Fa nptr in .Fa *endptr . (Thus, if .Fa *nptr is not .Ql \e0 but .Fa **endptr is .Ql \e0 on return, the entire string was valid.) .Sh RETURN VALUES The .Fn strtoi function always returns the closest value in the range specified by the .Fa lo and .Fa hi arguments. The .Fn strtol function returns the result of the conversion, unless the value would underflow or overflow. If an underflow occurs, .Fn strtol returns .Dv LONG_MIN , .Fn strtoll returns .Dv LLONG_MIN , and .Fn strtoimax returns .Dv INTMAX_MIN . If an overflow occurs, .Fn strtol returns .Dv LONG_MAX , .Fn strtoll returns .Dv LLONG_MAX , and .Fn strtoimax returns .Dv INTMAX_MAX . In these cases, .Va errno is set to .Er ERANGE . If the .Fa base argument is not supported then .Va errno is set to .Er EINVAL and the functions return 0.
p If no error occurs, .Va errno is left unchanged. This behavior (which is unlike most library functions) is guaranteed by the pertinent standards. .Sh EXAMPLES The .Fn strtoi function is the simplest to use: d -literal -offset indent int e; intmax_t lval = strtoi(buf, NULL, 0, 1, 99, &e); if (e) warn("conversion of `%s' to a number failed, using %jd", buf, lval); .Ed
p This will always return a number in .Dv [1..99] range no matter what the input is, and warn if the conversion failed.
p Because the return value of .Fn strtol cannot be used unambiguously to detect an error, .Va errno is left unchanged after a successful call. To ensure that a string is a valid number (i.e., in range and containing no trailing characters), clear .Va errno beforehand explicitly, then check it afterwards: d -literal -offset indent char *ep; long lval; ... errno = 0; lval = strtol(buf, \*[Am]ep, 10); if (buf[0] == '\e0' || *ep != '\e0') goto not_a_number; if (errno == ERANGE \*[Am]\*[Am] (lval == LONG_MAX || lval == LONG_MIN)) goto out_of_range; .Ed
p This example will accept .Dq 12 but not .Dq 12foo or .Dq 12\en . If trailing whitespace is acceptable, further checks must be done on .Va *ep ; alternately, use .Xr sscanf 3 .
p If .Fn strtol is being used instead of .Xr atoi 3 , error checking is further complicated because the desired return value is an .Li int rather than a .Li long ; however, on some architectures integers and long integers are the same size. Thus the following is necessary: d -literal -offset indent char *ep; int ival; long lval; ... errno = 0; lval = strtol(buf, \*[Am]ep, 10); if (buf[0] == '\e0' || *ep != '\e0') goto not_a_number; if ((errno == ERANGE \*[Am]\*[Am] (lval == LONG_MAX || lval == LONG_MIN)) || (lval \*[Gt] INT_MAX || lval \*[Lt] INT_MIN)) goto out_of_range; ival = lval; .Ed .Sh ERRORS l -tag -width Er t Bq Er EINVAL The .Ar base is not between 2 and 36 and does not contain the special value 0. t Bq Er ERANGE The given string was out of range; the value converted has been clamped. .El
p In addition to the above errors .Fn strtoi returns: l -tag -width Er t Bq Er ECANCELED The string did not contain any characters that could be converted. t Bq Er ENOTSUP The string contained non-numeric characters that did not get converted. In this case, .Fa endptr points to the first unconverted character. t Bq Er ERANGE The range given was invalid, i.e. .Fa lo \*[Gt] .Fa hi . .El .Sh SEE ALSO .Xr atof 3 , .Xr atoi 3 , .Xr atol 3 , .Xr atoll 3 , .Xr strtod 3 , .Xr strtou 3 , .Xr strtoul 3 , .Xr strtoull 3 , .Xr strtoumax 3 .Sh STANDARDS The .Fn strtol function conforms to .St -ansiC . The .Fn strtoll and .Fn strtoimax functions conform to .St -isoC-99 . The .Fn strtoi function appeared in .Nx 8 . .Sh BUGS Ignores the current locale.