1.\" 2.\" Copyright (c) 2004 Ted Unangst 3.\" 4.\" Permission to use, copy, modify, and distribute this software for any 5.\" purpose with or without fee is hereby granted, provided that the above 6.\" copyright notice and this permission notice appear in all copies. 7.\" 8.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 9.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 10.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 11.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 12.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 13.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 14.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 15.\" 16.Dd $Mdocdate: February 7 2016 $ 17.Dt STRTONUM 3C 18.Os 19.Sh NAME 20.Nm strtonum 21.Nd reliably convert string value to an integer 22.Sh LIBRARY 23.Lb libc 24.Sh SYNOPSIS 25.In stdlib.h 26.Ft long long 27.Fo strtonum 28.Fa "const char *nptr" 29.Fa "long long minval" 30.Fa "long long maxval" 31.Fa "const char **errstr" 32.Fc 33.Sh DESCRIPTION 34The 35.Fn strtonum 36function converts the string in 37.Fa nptr 38to a 39.Li long long 40value. 41The 42.Fn strtonum 43function was designed to facilitate safe, robust programming 44and overcome the shortcomings of the 45.Xr atoi 3C 46and 47.Xr strtol 3C 48family of interfaces. 49.Pp 50The string may begin with an arbitrary amount of whitespace 51.Pq as determined by Xr isspace 3C 52followed by a single optional 53.Ql + 54or 55.Ql - 56sign. 57.Pp 58The remainder of the string is converted to a 59.Li 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; this fact can be used to differentiate a successful return of 0 from 88an error. 89.Sh EXAMPLES 90Using 91.Fn strtonum 92correctly is meant to be simpler than the alternative functions. 93.Bd -literal -offset indent 94int iterations; 95const char *errstr; 96 97iterations = strtonum(optarg, 1, 64, &errstr); 98if (errstr != NULL) 99 errx(1, "number of iterations is %s: %s", errstr, optarg); 100.Ed 101.Pp 102The above example will guarantee that the value of iterations is between 1031 and 64 104.Pq inclusive . 105.Sh ERRORS 106.Bl -tag -width Er 107.It Er ERANGE 108The given string was out of range. 109.It Er EINVAL 110The given string did not consist solely of digit characters. 111.It 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 INTERFACE STABILITY 130.Sy Committed . 131.Sh MT-LEVEL 132.Sy Safe . 133.Sh SEE ALSO 134.Xr atof 3C , 135.Xr atoi 3C , 136.Xr atol 3C , 137.Xr atoll 3C , 138.Xr sscanf 3C , 139.Xr strtod 3C , 140.Xr strtol 3C , 141.Xr strtoul 3C 142.Sh STANDARDS 143.Fn strtonum 144is an 145.Ox 146extension. 147The existing alternatives, such as 148.Xr atoi 3C 149and 150.Xr strtol 3C , 151are either impossible or difficult to use safely. 152