1STRTOL(3)                  Linux Programmer's Manual                 STRTOL(3)
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3
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NAME

6       strtol, strtoll, strtoq - convert a string to a long integer
7

SYNOPSIS

9       #include <stdlib.h>
10
11       long int strtol(const char *nptr, char **endptr, int base);
12
13       long long int strtoll(const char *nptr, char **endptr, int base);
14
15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
16
17       strtoll(): XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE ||
18       _ISOC99_SOURCE; or cc -std=c99
19

DESCRIPTION

21       The strtol() function converts the initial part of the string  in  nptr
22       to  a  long  integer  value  according to the given base, which must be
23       between 2 and 36 inclusive, or be the special value 0.
24
25       The string may begin with an arbitrary amount of white space (as deter‐
26       mined by isspace(3)) followed by a single optional '+' or '-' sign.  If
27       base is zero or 16, the string may then include a "0x" prefix, and  the
28       number  will  be read in base 16; otherwise, a zero base is taken as 10
29       (decimal) unless the next character is '0', in which case it  is  taken
30       as 8 (octal).
31
32       The  remainder  of  the  string is converted to a long int value in the
33       obvious manner, stopping at the first character which is  not  a  valid
34       digit  in the given base.  (In bases above 10, the letter 'A' in either
35       upper or lower case represents 10, 'B' represents  11,  and  so  forth,
36       with 'Z' representing 35.)
37
38       If endptr is not NULL, strtol() stores the address of the first invalid
39       character in *endptr.  If there were no digits at all, strtol()  stores
40       the  original value of nptr in *endptr (and returns 0).  In particular,
41       if *nptr is not '\0' but **endptr is '\0' on return, the entire  string
42       is valid.
43
44       The  strtoll()  function  works  just  like  the  strtol() function but
45       returns a long long integer value.
46

RETURN VALUE

48       The strtol() function returns the result of the conversion, unless  the
49       value  would  underflow  or overflow.  If an underflow occurs, strtol()
50       returns LONG_MIN.  If an overflow occurs,  strtol()  returns  LONG_MAX.
51       In  both  cases,  errno is set to ERANGE.  Precisely the same holds for
52       strtoll()  (with  LLONG_MIN  and  LLONG_MAX  instead  of  LONG_MIN  and
53       LONG_MAX).
54

ERRORS

56       EINVAL (not in C99) The given base contains an unsupported value.
57
58       ERANGE The resulting value was out of range.
59
60       The  implementation  may also set errno to EINVAL in case no conversion
61       was performed (no digits seen, and 0 returned).
62

CONFORMING TO

64       strtol() conforms to SVr4, 4.3BSD, C89, C99 and POSIX.1-2001, and  str‐
65       toll() to C99 and POSIX.1-2001.
66

NOTES

68       Since  strtol()  can  legitimately  return  0,  LONG_MAX,  or  LONG_MIN
69       (LLONG_MAX or LLONG_MIN for strtoll()) on both success and failure, the
70       calling  program should set errno to 0 before the call, and then deter‐
71       mine if an error occurred by checking  whether  errno  has  a  non-zero
72       value after the call.
73
74       In  locales  other  than  the  "C"  locale,  other  strings may also be
75       accepted.  (For example, the thousands separator of the current  locale
76       may be supported.)
77
78       BSD also has
79
80           quad_t strtoq(const char *nptr, char **endptr, int base);
81
82       with completely analogous definition.  Depending on the wordsize of the
83       current architecture, this may be equivalent to strtoll()  or  to  str‐
84       tol().
85

EXAMPLE

87       The  program  shown  below demonstrates the use of strtol().  The first
88       command-line argument specifies a string  from  which  strtol()  should
89       parse  a  number.  The second (optional) argument specifies the base to
90       be used for the conversion.  (This argument  is  converted  to  numeric
91       form  using atoi(3), a function that performs no error checking and has
92       a simpler interface than strtol().)  Some examples of the results  pro‐
93       duced by this program are the following:
94
95           $ ./a.out 123
96           strtol() returned 123
97           $ ./a.out '    123'
98           strtol() returned 123
99           $ ./a.out 123abc
100           strtol() returned 123
101           Further characters after number: abc
102           $ ./a.out 123abc 55
103           strtol: Invalid argument
104           $ ./a.out ''
105           No digits were found
106           $ ./a.out 4000000000
107           strtol: Numerical result out of range
108
109   Program source
110
111       #include <stdlib.h>
112       #include <limits.h>
113       #include <stdio.h>
114       #include <errno.h>
115
116       int
117       main(int argc, char *argv[])
118       {
119           int base;
120           char *endptr, *str;
121           long val;
122
123           if (argc < 2) {
124               fprintf(stderr, "Usage: %s str [base]\n", argv[0]);
125               exit(EXIT_FAILURE);
126           }
127
128           str = argv[1];
129           base = (argc > 2) ? atoi(argv[2]) : 10;
130
131           errno = 0;    /* To distinguish success/failure after call */
132           val = strtol(str, &endptr, base);
133
134           /* Check for various possible errors */
135
136           if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
137                   || (errno != 0 && val == 0)) {
138               perror("strtol");
139               exit(EXIT_FAILURE);
140           }
141
142           if (endptr == str) {
143               fprintf(stderr, "No digits were found\n");
144               exit(EXIT_FAILURE);
145           }
146
147           /* If we got here, strtol() successfully parsed a number */
148
149           printf("strtol() returned %ld\n", val);
150
151           if (*endptr != '\0')        /* Not necessarily an error... */
152               printf("Further characters after number: %s\n", endptr);
153
154           exit(EXIT_SUCCESS);
155       }
156

SEE ALSO

158       atof(3), atoi(3), atol(3), strtod(3), strtoul(3)
159

COLOPHON

161       This  page  is  part of release 3.22 of the Linux man-pages project.  A
162       description of the project, and information about reporting  bugs,  can
163       be found at http://www.kernel.org/doc/man-pages/.
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167GNU                               2007-07-26                         STRTOL(3)
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