1.\" $NetBSD: strtoul.3,v 1.25 2009/12/02 12:50:27 pooka Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" Chris Torek and the American National Standards Committee X3, 8.\" on Information Processing Systems. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" from: @(#)strtoul.3 8.1 (Berkeley) 6/4/93 35.\" 36.Dd December 2, 2009 37.Dt STRTOUL 3 38.Os 39.Sh NAME 40.Nm strtoul , 41.Nm strtoull , 42.Nm strtoumax , 43.Nm strtouq 44.Nd convert a string to an unsigned long, unsigned long long, uintmax_t or uquad_t integer 45.Sh LIBRARY 46.Lb libc 47.Sh SYNOPSIS 48.In stdlib.h 49.In limits.h 50.Ft unsigned long int 51.Fn strtoul "const char * restrict nptr" "char ** restrict endptr" "int base" 52.Ft unsigned long long int 53.Fn strtoull "const char * restrict nptr" "char ** restrict endptr" "int base" 54.Pp 55.In inttypes.h 56.Ft uintmax_t 57.Fn strtoumax "const char * restrict nptr" "char ** restrict endptr" "int base" 58.Pp 59.In sys/types.h 60.In stdlib.h 61.In limits.h 62.Ft u_quad_t 63.Fn strtouq "const char * restrict nptr" "char ** restrict endptr" "int base" 64.Sh DESCRIPTION 65The 66.Fn strtoul 67function 68converts the string in 69.Fa nptr 70to an 71.Ft unsigned long int 72value. 73The 74.Fn strtoull 75function 76converts the string in 77.Fa nptr 78to an 79.Ft unsigned long long int 80value. 81The 82.Fn strtoumax 83function 84converts the string in 85.Fa nptr 86to an 87.Ft uintmax_t 88value. 89The 90.Fn strtouq 91function 92converts the string in 93.Fa nptr 94to a 95.Ft u_quad_t 96value. 97The conversion is done according to the given 98.Fa base , 99which must be between 2 and 36 inclusive, 100or be the special value 0. 101.Pp 102The string may begin with an arbitrary amount of white space 103(as determined by 104.Xr isspace 3 ) 105followed by a single optional 106.Ql + 107or 108.Ql - 109sign. 110If 111.Fa base 112is zero or 16, 113the string may then include a 114.Ql 0x 115prefix, 116and the number will be read in base 16; otherwise, a zero 117.Fa base 118is taken as 10 (decimal) unless the next character is 119.Ql 0 , 120in which case it is taken as 8 (octal). 121.Pp 122The remainder of the string is converted to an 123.Em unsigned long 124value in the obvious manner, 125stopping at the end of the string 126or at the first character that does not produce a valid digit 127in the given base. 128(In bases above 10, the letter 129.Ql A 130in either upper or lower case 131represents 10, 132.Ql B 133represents 11, and so forth, with 134.Ql Z 135representing 35.) 136.Pp 137If 138.Fa endptr 139is non-nil, 140.Fn strtoul 141stores the address of the first invalid character in 142.Fa *endptr . 143If there were no digits at all, however, 144.Fn strtoul 145stores the original value of 146.Fa nptr 147in 148.Fa *endptr . 149(Thus, if 150.Fa *nptr 151is not 152.Ql \e0 153but 154.Fa **endptr 155is 156.Ql \e0 157on return, the entire string was valid.) 158.Sh RETURN VALUES 159The 160.Fn strtoul 161function 162returns either the result of the conversion 163or, if there was a leading minus sign, 164the negation of the result of the conversion, 165unless the original (non-negated) value would overflow; 166in the latter case, 167.Fn strtoul 168returns 169.Dv ULONG_MAX , 170.Fn strtoull 171returns 172.Dv ULLONG_MAX , 173.Fn strtoumax 174returns 175.Dv UINTMAX_MAX , 176.Fn strtouq 177returns 178.Dv UQUAD_MAX , 179and the global variable 180.Va errno 181is set to 182.Er ERANGE . 183.Pp 184There is no way to determine if 185.Fn strtoul 186has processed a negative number (and returned an unsigned value) short of 187examining the string in 188.Fa nptr 189directly. 190If the 191.Fa base 192argument is not supported then 193.Va errno 194is set to 195.Er EINVAL 196and the functions return 0. 197.Pp 198If no error occurs, 199.Va errno 200is left unchanged. 201This behavior (which is unlike most library functions) is guaranteed 202by the pertinent standards. 203.Sh EXAMPLES 204Because the return value of 205.Fn strtoul 206cannot be used unambiguously to detect an error, 207.Va errno 208is left unchanged after a successful call. 209To ensure that a string is a valid number (i.e., in range and containing no 210trailing characters), clear 211.Va errno 212beforehand explicitly, then check it afterwards: 213.Bd -literal -offset indent 214char *ep; 215unsigned long ulval; 216 217\&... 218 219errno = 0; 220ulval = strtoul(buf, \*[Am]ep, 10); 221if (buf[0] == '\e0' || *ep != '\e0') 222 goto not_a_number; 223if (errno == ERANGE \*[Am]\*[Am] ulval == ULONG_MAX) 224 goto out_of_range; 225.Ed 226.Pp 227This example will accept 228.Dq 12 229but not 230.Dq 12foo 231or 232.Dq 12\en . 233If trailing whitespace is acceptable, further checks must be done on 234.Va *ep ; 235alternately, use 236.Xr sscanf 3 . 237.Sh ERRORS 238.Bl -tag -width Er 239.It Bq Er EINVAL 240The 241.Ar base 242is not between 2 and 36 and does not contain the special value 0. 243.It Bq Er ERANGE 244The given string was out of range; the value converted has been clamped. 245.El 246.Sh SEE ALSO 247.Xr strtoimax 3 , 248.Xr strtol 3 , 249.Xr strtoll 3 250.Sh STANDARDS 251The 252.Fn strtoul 253function 254conforms to 255.St -ansiC . 256The 257.Fn strtoull 258and 259.Fn strtoumax 260functions conform to 261.St -isoC-99 . 262.Sh BUGS 263Ignores the current locale. 264