man3/strtol.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   2 .\"
   3 .\" Permission is granted to make and distribute verbatim copies of this
   4 .\" manual provided the copyright notice and this permission notice are
   5 .\" preserved on all copies.
   6 .\"
   7 .\" Permission is granted to copy and distribute modified versions of this
   8 .\" manual under the conditions for verbatim copying, provided that the
   9 .\" entire resulting derived work is distributed under the terms of a
  10 .\" permission notice identical to this one.
  11 .\"
  12 .\" Since the Linux kernel and libraries are constantly changing, this
  13 .\" manual page may be incorrect or out-of-date.  The author(s) assume no
  14 .\" responsibility for errors or omissions, or for damages resulting from
  15 .\" the use of the information contained herein.  The author(s) may not
  16 .\" have taken the same level of care in the production of this manual,
  17 .\" which is licensed free of charge, as they might when working
  18 .\" professionally.
  19 .\"
  20 .\" Formatted or processed versions of this manual, if unaccompanied by
  21 .\" the source, must acknowledge the copyright and authors of this work.
  22 .\"
  23 .\" References consulted:
  24 .\"     Linux libc source code
  25 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  26 .\"     386BSD man pages
  27 .\" Modified Sun Jul 25 10:53:39 1993 by Rik Faith (faith@cs.unc.edu)
  28 .\" Added correction due to nsd@bbc.com (Nick Duffek) - aeb, 950610
  29 .TH STRTOL 3  2013-02-10 "GNU" "Linux Programmer's Manual"
  30 .SH NAME
  31 strtol, strtoll, strtoq \- convert a string to a long integer
  32 .SH SYNOPSIS
  33 .nf
  34 .B #include <stdlib.h>
  35 .sp
  36 .BI "long int strtol(const char *" nptr ", char **" endptr ", int " base );
  37 .sp
  38 .BI "long long int strtoll(const char *" nptr ", char **" endptr \
  39 ", int " base );
  40 .fi
  41 .sp
  42 .in -4n
  43 Feature Test Macro Requirements for glibc (see
  44 .BR feature_test_macros (7)):
  45 .in
  46 .sp
  47 .ad l
  48 .BR strtoll ():
  49 .RS 4
  50 XOPEN_SOURCE\ >=\ 600 || _BSD_SOURCE || _SVID_SOURCE || _ISOC99_SOURCE ||
  51 _POSIX_C_SOURCE\ >=\ 200112L;
  52 .br
  53 or
  54 .I cc\ -std=c99
  55 .RE
  56 .ad
  57 .SH DESCRIPTION
  58 The
  59 .BR strtol ()
  60 function converts the initial part of the string
  61 in \fInptr\fP to a long integer value according to the given \fIbase\fP,
  62 which must be between 2 and 36 inclusive, or be the special value 0.
  63 .PP
  64 The string may begin with an arbitrary amount of white space (as
  65 determined by
  66 .BR isspace (3))
  67 followed by a single optional \(aq+\(aq or \(aq\-\(aq sign.
  68 If \fIbase\fP is zero or 16, the string may then include a
  69 "0x" prefix, and the number will be read in base 16; otherwise, a
  70 zero \fIbase\fP is taken as 10 (decimal) unless the next character
  71 is \(aq0\(aq, in which case it is taken as 8 (octal).
  72 .PP
  73 The remainder of the string is converted to a
  74 .I long int
  75 value
  76 in the obvious manner, stopping at the first character which is not a
  77 valid digit in the given base.
  78 (In bases above 10, the letter \(aqA\(aq in
  79 either upper or lower case represents 10, \(aqB\(aq represents 11, and so
  80 forth, with \(aqZ\(aq representing 35.)
  81 .PP
  82 If \fIendptr\fP is not NULL,
  83 .BR strtol ()
  84 stores the address of the
  85 first invalid character in \fI*endptr\fP.
  86 If there were no digits at
  87 all,
  88 .BR strtol ()
  89 stores the original value of \fInptr\fP in
  90 \fI*endptr\fP (and returns 0).
  91 In particular, if \fI*nptr\fP is not \(aq\\0\(aq but \fI**endptr\fP
  92 is \(aq\\0\(aq on return, the entire string is valid.
  93 .PP
  94 The
  95 .BR strtoll ()
  96 function works just like the
  97 .BR strtol ()
  98 function but returns a long long integer value.
  99 .SH "RETURN VALUE"
 100 The
 101 .BR strtol ()
 102 function returns the result of the conversion,
 103 unless the value would underflow or overflow.
 104 If an underflow occurs,
 105 .BR strtol ()
 106 returns
 107 .BR LONG_MIN .
 108 If an overflow occurs,
 109 .BR strtol ()
 110 returns
 111 .BR LONG_MAX .
 112 In both cases, \fIerrno\fP is set to
 113 .BR ERANGE .
 114 Precisely the same holds for
 115 .BR strtoll ()
 116 (with
 117 .B LLONG_MIN
 118 and
 119 .B LLONG_MAX
 120 instead of
 121 .B LONG_MIN
 122 and
 123 .BR LONG_MAX ).
 124 .SH ERRORS
 125 .TP
 126 .B EINVAL
 127 (not in C99)
 128 The given
 129 .I base
 130 contains an unsupported value.
 131 .TP
 132 .B ERANGE
 133 The resulting value was out of range.
 134 .LP
 135 The implementation may also set \fIerrno\fP to \fBEINVAL\fP in case
 136 no conversion was performed (no digits seen, and 0 returned).
 137 .SH "CONFORMING TO"
 138 .BR strtol ()
 139 conforms to SVr4, 4.3BSD, C89, C99 and POSIX.1-2001, and
 140 .BR strtoll ()
 141 to C99 and POSIX.1-2001.
 142 .SH NOTES
 143 Since
 144 .BR strtol ()
 145 can legitimately return 0,
 146 .BR LONG_MAX ,
 147 or
 148 .B LONG_MIN
 149 .RB ( LLONG_MAX
 150 or
 151 .B LLONG_MIN
 152 for
 153 .BR strtoll ())
 154 on both success and failure, the calling program should set
 155 .I errno
 156 to 0 before the call,
 157 and then determine if an error occurred by checking whether
 158 .I errno
 159 has a nonzero value after the call.
 160
 161 According to POSIX.1-2001,
 162 in locales other than the "C" and "POSIX",
 163 these functions may accept other,
 164 implementation-defined numeric strings.
 165
 166 other implementation-defined strings may be accepted.
 167 (For example, the thousands separator of the current locale may be
 168 supported.)
 169 .LP
 170 BSD also has
 171 .sp
 172 .in +4n
 173 .nf
 174 .BI "quad_t strtoq(const char *" nptr ", char **" endptr ", int " base );
 175 .sp
 176 .in
 177 .fi
 178 with completely analogous definition.
 179 Depending on the wordsize of the current architecture, this
 180 may be equivalent to
 181 .BR strtoll ()
 182 or to
 183 .BR strtol ().
 184 .SH EXAMPLE
 185 The program shown below demonstrates the use of
 186 .BR strtol ().
 187 The first command-line argument specifies a string from which
 188 .BR strtol ()
 189 should parse a number.
 190 The second (optional) argument specifies the base to be used for
 191 the conversion.
 192 (This argument is converted to numeric form using
 193 .BR atoi (3),
 194 a function that performs no error checking and
 195 has a simpler interface than
 196 .BR strtol ().)
 197 Some examples of the results produced by this program are the following:
 198 .in +4n
 199 .nf
 200
 201 .RB "$" " ./a.out 123"
 202 strtol() returned 123
 203 .RB "$" " ./a.out \(aq    123\(aq"
 204 strtol() returned 123
 205 .RB "$" " ./a.out 123abc"
 206 strtol() returned 123
 207 Further characters after number: abc
 208 .RB "$" " ./a.out 123abc 55"
 209 strtol: Invalid argument
 210 .RB "$" " ./a.out \(aq\(aq"
 211 No digits were found
 212 .RB "$" " ./a.out 4000000000"
 213 strtol: Numerical result out of range
 214 .fi
 215 .in
 216 .SS Program source
 217 \&
 218 .nf
 219 #include <stdlib.h>
 220 #include <limits.h>
 221 #include <stdio.h>
 222 #include <errno.h>
 223
 224 int
 225 main(int argc, char *argv[])
 226 {
 227     int base;
 228     char *endptr, *str;
 229     long val;
 230
 231     if (argc < 2) {
 232         fprintf(stderr, "Usage: %s str [base]\\n", argv[0]);
 233         exit(EXIT_FAILURE);
 234     }
 235
 236     str = argv[1];
 237     base = (argc > 2) ? atoi(argv[2]) : 10;
 238
 239     errno = 0;    /* To distinguish success/failure after call */
 240     val = strtol(str, &endptr, base);
 241
 242     /* Check for various possible errors */
 243
 244     if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
 245             || (errno != 0 && val == 0)) {
 246         perror("strtol");
 247         exit(EXIT_FAILURE);
 248     }
 249
 250     if (endptr == str) {
 251         fprintf(stderr, "No digits were found\\n");
 252         exit(EXIT_FAILURE);
 253     }
 254
 255     /* If we got here, strtol() successfully parsed a number */
 256
 257     printf("strtol() returned %ld\\n", val);
 258
 259     if (*endptr != \(aq\\0\(aq)        /* Not necessarily an error... */
 260         printf("Further characters after number: %s\\n", endptr);
 261
 262     exit(EXIT_SUCCESS);
 263 }
 264 .fi
 265 .SH "SEE ALSO"
 266 .BR atof (3),
 267 .BR atoi (3),
 268 .BR atol (3),
 269 .BR strtod (3),
 270 .BR strtoul (3)