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