1.\" $OpenBSD: strtonum.3,v 1.19 2022/09/11 06:38:11 jmc Exp $ 2.\" 3.\" Copyright (c) 2004 Ted Unangst 4.\" 5.\" Permission to use, copy, modify, and distribute this software for any 6.\" purpose with or without fee is hereby granted, provided that the above 7.\" copyright notice and this permission notice appear in all copies. 8.\" 9.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16.\" 17.Dd $Mdocdate: September 11 2022 $ 18.Dt STRTONUM 3 19.Os 20.Sh NAME 21.Nm strtonum 22.Nd reliably convert string value to an integer 23.Sh SYNOPSIS 24.In stdlib.h 25.Ft long long 26.Fo strtonum 27.Fa "const char *nptr" 28.Fa "long long minval" 29.Fa "long long maxval" 30.Fa "const char **errstr" 31.Fc 32.Sh DESCRIPTION 33The 34.Fn strtonum 35function converts the string in 36.Fa nptr 37to a 38.Vt long long 39value. 40The 41.Fn strtonum 42function was designed to facilitate safe, robust programming 43and overcome the shortcomings of the 44.Xr atoi 3 45and 46.Xr strtol 3 47family of interfaces. 48.Pp 49The string may begin with an arbitrary amount of whitespace 50(as determined by 51.Xr isspace 3 ) 52followed by a single optional 53.Ql + 54or 55.Ql - 56sign. 57.Pp 58The remainder of the string is converted to a 59.Vt long long 60value according to base 10. 61.Pp 62The value obtained is then checked against the provided 63.Fa minval 64and 65.Fa maxval 66bounds. 67If 68.Fa errstr 69is non-null, 70.Fn strtonum 71stores an error string in 72.Fa *errstr 73indicating the failure. 74.Sh RETURN VALUES 75The 76.Fn strtonum 77function returns the result of the conversion, 78unless the value would exceed the provided bounds or is invalid. 79On error, 0 is returned, 80.Va errno 81is set, and 82.Fa errstr 83will point to an error message. 84.Fa *errstr 85will be set to 86.Dv NULL 87on success; 88this fact can be used to differentiate 89a successful return of 0 from an error. 90.Sh EXAMPLES 91Using 92.Fn strtonum 93correctly is meant to be simpler than the alternative functions. 94.Bd -literal -offset indent 95int iterations; 96const char *errstr; 97 98iterations = strtonum(optarg, 1, 64, &errstr); 99if (errstr != NULL) 100 errx(1, "number of iterations is %s: %s", errstr, optarg); 101.Ed 102.Pp 103The above example will guarantee that the value of iterations is between 1041 and 64 (inclusive). 105.Sh ERRORS 106.Bl -tag -width Er 107.It Bq Er ERANGE 108The given string was out of range. 109.It Bq Er EINVAL 110The given string did not consist solely of digit characters. 111.It Bq Er EINVAL 112.Ar minval 113was larger than 114.Ar maxval . 115.El 116.Pp 117If an error occurs, 118.Fa errstr 119will be set to one of the following strings: 120.Pp 121.Bl -tag -width "too largeXX" -compact 122.It Qq too large 123The result was larger than the provided maximum value. 124.It Qq too small 125The result was smaller than the provided minimum value. 126.It Qq invalid 127The string did not consist solely of digit characters. 128.El 129.Sh SEE ALSO 130.Xr atof 3 , 131.Xr atoi 3 , 132.Xr atol 3 , 133.Xr atoll 3 , 134.Xr sscanf 3 , 135.Xr strtod 3 , 136.Xr strtol 3 , 137.Xr strtoul 3 138.Sh STANDARDS 139.Fn strtonum 140is an 141.Ox 142extension. 143The existing alternatives, such as 144.Xr atoi 3 145and 146.Xr strtol 3 , 147are either impossible or difficult to use safely. 148.Sh HISTORY 149The 150.Fn strtonum 151function first appeared in 152.Ox 3.6 . 153