man3/strtol.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  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  2007-07-26 "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 .B "long int"
  37 .BI "strtol(const char *" nptr ", char **" endptr ", int " base );
  38 .sp
  39 .B "long long int"
  40 .BI "strtoll(const char *" nptr ", char **" endptr ", int " base );
  41 .fi
  42 .sp
  43 .in -4n
  44 Feature Test Macro Requirements for glibc (see
  45 .BR feature_test_macros (7)):
  46 .in
  47 .sp
  48 .ad l
  49 .BR strtoll ():
  50 XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE || _ISOC99_SOURCE; or
  51 .I cc\ -std=c99
  52 .ad b
  53 .SH DESCRIPTION
  54 The
  55 .BR strtol ()
  56 function converts the initial part of the string
  57 in \fInptr\fP to a long integer value according to the given \fIbase\fP,
  58 which must be between 2 and 36 inclusive, or be the special value 0.
  59 .PP
  60 The string may begin with an arbitrary amount of white space (as
  61 determined by
  62 .BR isspace (3))
  63 followed by a single optional '+' or '\-' sign.
  64 If \fIbase\fP is zero or 16, the string may then include a
  65 "0x" prefix, and the number will be read in base 16; otherwise, a
  66 zero \fIbase\fP is taken as 10 (decimal) unless the next character
  67 is '0', in which case it is taken as 8 (octal).
  68 .PP
  69 The remainder of the string is converted to a
  70 .I long int
  71 value
  72 in the obvious manner, stopping at the first character which is not a
  73 valid digit in the given base.
  74 (In bases above 10, the letter 'A' in
  75 either upper or lower case represents 10, 'B' represents 11, and so
  76 forth, with 'Z' representing 35.)
  77 .PP
  78 If \fIendptr\fP is not NULL,
  79 .BR strtol ()
  80 stores the address of the
  81 first invalid character in \fI*endptr\fP.
  82 If there were no digits at
  83 all,
  84 .BR strtol ()
  85 stores the original value of \fInptr\fP in
  86 \fI*endptr\fP (and returns 0).
  87 In particular, if \fI*nptr\fP is not '\\0' but \fI**endptr\fP
  88 is '\\0' on return, the entire string is valid.
  89 .PP
  90 The
  91 .BR strtoll ()
  92 function works just like the
  93 .BR strtol ()
  94 function but returns a long long integer value.
  95 .SH "RETURN VALUE"
  96 The
  97 .BR strtol ()
  98 function returns the result of the conversion,
  99 unless the value would underflow or overflow.
 100 If an underflow occurs,
 101 .BR strtol ()
 102 returns
 103 .BR LONG_MIN .
 104 If an overflow occurs,
 105 .BR strtol ()
 106 returns
 107 .BR LONG_MAX .
 108 In both cases, \fIerrno\fP is set to
 109 .BR ERANGE .
 110 Precisely the same holds for
 111 .BR strtoll ()
 112 (with
 113 .B LLONG_MIN
 114 and
 115 .B LLONG_MAX
 116 instead of
 117 .B LONG_MIN
 118 and
 119 .BR LONG_MAX ).
 120 .SH ERRORS
 121 .TP
 122 .B EINVAL
 123 (not in C99)
 124 The given
 125 .I base
 126 contains an unsupported value.
 127 .TP
 128 .B ERANGE
 129 The resulting value was out of range.
 130 .LP
 131 The implementation may also set \fIerrno\fP to \fBEINVAL\fP in case
 132 no conversion was performed (no digits seen, and 0 returned).
 133 .SH "CONFORMING TO"
 134 .BR strtol ()
 135 conforms to SVr4, 4.3BSD, C89, C99 and POSIX.1-2001, and
 136 .BR strtoll ()
 137 to C99 and POSIX.1-2001.
 138 .SH NOTES
 139 Since
 140 .BR strtol ()
 141 can legitimately return 0,
 142 .BR LONG_MAX ,
 143 or
 144 .B LONG_MIN
 145 .RB ( LLONG_MAX
 146 or
 147 .B LLONG_MIN
 148 for
 149 .BR strtoll ())
 150 on both success and failure, the calling program should set
 151 .I errno
 152 to 0 before the call,
 153 and then determine if an error occurred by checking whether
 154 .I errno
 155 has a non-zero value after the call.
 156
 157 In locales other than the "C" locale, other strings may also be accepted.
 158 (For example, the thousands separator of the current locale may be
 159 supported.)
 160 .LP
 161 BSD also has
 162 .sp
 163 .in +4n
 164 .nf
 165 .B "quad_t"
 166 .BI "strtoq(const char *" nptr ", char **" endptr ", int " base );
 167 .sp
 168 .in -4n
 169 .fi
 170 with completely analogous definition.
 171 Depending on the wordsize of the current architecture, this
 172 may be equivalent to
 173 .BR strtoll ()
 174 or to
 175 .BR strtol ().
 176 .SH EXAMPLE
 177 The program shown below demonstrates the use of
 178 .BR strtol ().
 179 The first command line argument specifies a string from which
 180 .BR strtol ()
 181 should parse a number.
 182 The second (optional) argument specifies the base to be used for
 183 the conversion.
 184 (This argument is converted to numeric form using
 185 .BR atoi (3),
 186 a function that performs no error checking and
 187 has a simpler interface than
 188 .BR strtol ().)
 189 Some examples of the results produced by this program are the following:
 190 .in +0.25i
 191 .nf
 192
 193 $ ./a.out 123
 194 strtol() returned 123
 195 $ ./a.out '    123'
 196 strtol() returned 123
 197 $ ./a.out 123abc
 198 strtol() returned 123
 199 Further characters after number: abc
 200 $ ./a.out 123abc 55
 201 strtol: Invalid argument
 202 $ ./a.out ''
 203 No digits were found
 204 $ ./a.out 4000000000
 205 strtol: Numerical result out of range
 206
 207 .fi
 208 .in -0.25i
 209 The source code of the program is as follows:
 210 .nf
 211
 212 #include <stdlib.h>
 213 #include <limits.h>
 214 #include <stdio.h>
 215 #include <errno.h>
 216
 217 int
 218 main(int argc, char *argv[])
 219 {
 220     int base;
 221     char *endptr, *str;
 222     long val;
 223
 224     if (argc < 2) {
 225         fprintf(stderr, "Usage: %s str [base]\\n", argv[0]);
 226         exit(EXIT_FAILURE);
 227     }
 228
 229     str = argv[1];
 230     base = (argc > 2) ? atoi(argv[2]) : 10;
 231
 232     errno = 0;    /* To distinguish success/failure after call */
 233     val = strtol(str, &endptr, base);
 234
 235     /* Check for various possible errors */
 236
 237     if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
 238             || (errno != 0 && val == 0)) {
 239         perror("strtol");
 240         exit(EXIT_FAILURE);
 241     }
 242
 243     if (endptr == str) {
 244         fprintf(stderr, "No digits were found\\n");
 245         exit(EXIT_FAILURE);
 246     }
 247
 248     /* If we got here, strtol() successfully parsed a number */
 249
 250     printf("strtol() returned %ld\\n", val);
 251
 252     if (*endptr != '\\0')        /* Not necessarily an error... */
 253         printf("Further characters after number: %s\\n", endptr);
 254
 255     exit(EXIT_SUCCESS);
 256 }
 257 .fi
 258 .SH "SEE ALSO"
 259 .BR atof (3),
 260 .BR atoi (3),
 261 .BR atol (3),
 262 .BR strtod (3),
 263 .BR strtoul (3)