1STRTOL(3) Linux Programmer's Manual STRTOL(3)
2
6 strtol, strtoll, strtoq - convert a string to a long integer
7
9 #include <stdlib.h>
10 long int strtol(const char *nptr, char **endptr, int base);
12 long long int strtoll(const char *nptr, char **endptr, int base);
14 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
16 strtoll():
18 XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE ||
19 _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
20 or cc -std=c99
21
23 The strtol() function converts the initial part of the string in nptr
24 to a long integer value according to the given base, which must be
25 between 2 and 36 inclusive, or be the special value 0.
26 The string may begin with an arbitrary amount of white space (as deter‐
28 mined by isspace(3)) followed by a single optional '+' or '-' sign. If
29 base is zero or 16, the string may then include a "0x" prefix, and the
30 number will be read in base 16; otherwise, a zero base is taken as 10
31 (decimal) unless the next character is '0', in which case it is taken
32 as 8 (octal).
33 The remainder of the string is converted to a long int value in the
35 obvious manner, stopping at the first character which is not a valid
36 digit in the given base. (In bases above 10, the letter 'A' in either
37 upper or lower case represents 10, 'B' represents 11, and so forth,
38 with 'Z' representing 35.)
39 If endptr is not NULL, strtol() stores the address of the first invalid
41 character in *endptr. If there were no digits at all, strtol() stores
42 the original value of nptr in *endptr (and returns 0). In particular,
43 if *nptr is not '\0' but **endptr is '\0' on return, the entire string
44 is valid.
45 The strtoll() function works just like the strtol() function but
47 returns a long long integer value.
48
50 The strtol() function returns the result of the conversion, unless the
51 value would underflow or overflow. If an underflow occurs, strtol()
52 returns LONG_MIN. If an overflow occurs, strtol() returns LONG_MAX.
53 In both cases, errno is set to ERANGE. Precisely the same holds for
54 strtoll() (with LLONG_MIN and LLONG_MAX instead of LONG_MIN and
55 LONG_MAX).
56
58 EINVAL (not in C99) The given base contains an unsupported value.
59 ERANGE The resulting value was out of range.
61 The implementation may also set errno to EINVAL in case no conversion
63 was performed (no digits seen, and 0 returned).
64
66 strtol() conforms to SVr4, 4.3BSD, C89, C99 and POSIX.1-2001, and str‐
67 toll() to C99 and POSIX.1-2001.
68
70 Since strtol() can legitimately return 0, LONG_MAX, or LONG_MIN
71 (LLONG_MAX or LLONG_MIN for strtoll()) on both success and failure, the
72 calling program should set errno to 0 before the call, and then deter‐
73 mine if an error occurred by checking whether errno has a nonzero value
74 after the call.
75 According to POSIX.1-2001, in locales other than the "C" and "POSIX",
77 these functions may accept other, implementation-defined numeric
78 strings.
79 BSD also has
81 quad_t strtoq(const char *nptr, char **endptr, int base);
83 with completely analogous definition. Depending on the wordsize of the
85 current architecture, this may be equivalent to strtoll() or to str‐
86 tol().
87
89 The program shown below demonstrates the use of strtol(). The first
90 command-line argument specifies a string from which strtol() should
91 parse a number. The second (optional) argument specifies the base to
92 be used for the conversion. (This argument is converted to numeric
93 form using atoi(3), a function that performs no error checking and has
94 a simpler interface than strtol().) Some examples of the results pro‐
95 duced by this program are the following:
96 $ ./a.out 123
98 strtol() returned 123
99 $ ./a.out ' 123'
100 strtol() returned 123
101 $ ./a.out 123abc
102 strtol() returned 123
103 Further characters after number: abc
104 $ ./a.out 123abc 55
105 strtol: Invalid argument
106 $ ./a.out ''
107 No digits were found
108 $ ./a.out 4000000000
109 strtol: Numerical result out of range
110 Program source
112 #include <stdlib.h>
114 #include <limits.h>
115 #include <stdio.h>
116 #include <errno.h>
117 int
119 main(int argc, char *argv[])
120 {
121 int base;
122 char *endptr, *str;
123 long val;
124 if (argc < 2) {
126 fprintf(stderr, "Usage: %s str [base]\n", argv[0]);
127 exit(EXIT_FAILURE);
128 }
129 str = argv[1];
131 base = (argc > 2) ? atoi(argv[2]) : 10;
132 errno = 0; /* To distinguish success/failure after call */
134 val = strtol(str, &endptr, base);
135 /* Check for various possible errors */
137 if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
139 || (errno != 0 && val == 0)) {
140 perror("strtol");
141 exit(EXIT_FAILURE);
142 }
143 if (endptr == str) {
145 fprintf(stderr, "No digits were found\n");
146 exit(EXIT_FAILURE);
147 }
148 /* If we got here, strtol() successfully parsed a number */
150 printf("strtol() returned %ld\n", val);
152 if (*endptr != '\0') /* Not necessarily an error... */
154 printf("Further characters after number: %s\n", endptr);
155 exit(EXIT_SUCCESS);
157 }
158
160 atof(3), atoi(3), atol(3), strtod(3), strtoul(3)
161
163 This page is part of release 3.53 of the Linux man-pages project. A
164 description of the project, and information about reporting bugs, can
165 be found at http://www.kernel.org/doc/man-pages/.
166GNU 2013-02-10 STRTOL(3)