From 754bbf7a25a8dda49b5d08ef0d0443bbf5af0e36 Mon Sep 17 00:00:00 2001 From: Craig Jennings Date: Sun, 7 Apr 2024 13:41:34 -0500 Subject: new repository --- devdocs/c/string%2Fbyte%2Fstrtol.html | 105 ++++++++++++++++++++++++++++++++++ 1 file changed, 105 insertions(+) create mode 100644 devdocs/c/string%2Fbyte%2Fstrtol.html (limited to 'devdocs/c/string%2Fbyte%2Fstrtol.html') diff --git a/devdocs/c/string%2Fbyte%2Fstrtol.html b/devdocs/c/string%2Fbyte%2Fstrtol.html new file mode 100644 index 00000000..5b16e65b --- /dev/null +++ b/devdocs/c/string%2Fbyte%2Fstrtol.html @@ -0,0 +1,105 @@ +

strtol, strtoll

Defined in header <stdlib.h> 
long      strtol( const char          *str, char          **str_end, int base );
 (until C99) 
long      strtol( const char *restrict str, char **restrict str_end, int base );
+		 (since C99) 
long long strtoll( const char *restrict str, char **restrict str_end, int base );
+		 (since C99)

Interprets an integer value in a byte string pointed to by str.

+

Discards any whitespace characters (as identified by calling isspace) until the first non-whitespace character is found, then takes as many characters as possible to form a valid base-n (where n=base) integer number representation and converts them to an integer value. The valid integer value consists of the following parts:

+

The set of valid values for base is {0,2,3,...,36}. The set of valid digits for base-2 integers is {0,1}, for base-3 integers is {0,1,2}, and so on. For bases larger than 10, valid digits include alphabetic characters, starting from Aa for base-11 integer, to Zz for base-36 integer. The case of the characters is ignored.

+

Additional numeric formats may be accepted by the currently installed C locale.

+

If the value of base is ​0​, the numeric base is auto-detected: if the prefix is 0, the base is octal, if the prefix is 0x or 0X, the base is hexadecimal, otherwise the base is decimal.

+

If the minus sign was part of the input sequence, the numeric value calculated from the sequence of digits is negated as if by unary minus in the result type.

+

The functions set the pointer pointed to by str_end to point to the character past the last numeric character interpreted. If str_end is a null pointer, it is ignored.

+

If the str is empty or does not have the expected form, no conversion is performed, and (if str_end is not a null pointer) the value of str is stored in the object pointed to by str_end.

+

Parameters

+ + + +
str - pointer to the null-terminated byte string to be interpreted
str_end - pointer to a pointer to character.
base - base of the interpreted integer value

Return value

Example

#include <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+ 
+int main(void)
+{
+    // parsing with error handling
+    const char *p = "10 200000000000000000000000000000 30 -40 junk";
+    printf("Parsing '%s':\n", p);
+ 
+    for (;;)
+    {
+        // errno can be set to any non-zero value by a library function call
+        // regardless of whether there was an error, so it needs to be cleared
+        // in order to check the error set by strtol
+        errno = 0;
+        char *end;
+        const long i = strtol(p, &end, 10);
+        if (p == end)
+            break;
+ 
+        const bool range_error = errno == ERANGE;
+        printf("Extracted '%.*s', strtol returned %ld.", (int)(end-p), p, i);
+        p = end;
+ 
+        if (range_error)
+            printf("\n --> Range error occurred.");
+ 
+        putchar('\n');
+    }
+ 
+    printf("Unextracted leftover: '%s'\n\n", p);
+ 
+    // parsing without error handling
+    printf("\"1010\" in binary  --> %ld\n", strtol("1010", NULL, 2));
+    printf("\"12\"   in octal   --> %ld\n", strtol("12",   NULL, 8));
+    printf("\"A\"    in hex     --> %ld\n", strtol("A",    NULL, 16));
+    printf("\"junk\" in base-36 --> %ld\n", strtol("junk", NULL, 36));
+    printf("\"012\"  in auto-detected base --> %ld\n", strtol("012",  NULL, 0));
+    printf("\"0xA\"  in auto-detected base --> %ld\n", strtol("0xA",  NULL, 0));
+    printf("\"junk\" in auto-detected base --> %ld\n", strtol("junk", NULL, 0));
+}

Possible output:

+
Parsing '10 200000000000000000000000000000 30 -40 junk':
+Extracted '10', strtol returned 10.
+Extracted ' 200000000000000000000000000000', strtol returned 9223372036854775807.
+ --> Range error occurred.
+Extracted ' 30', strtol returned 30.
+Extracted ' -40', strtol returned -40.
+Unextracted leftover: ' junk'
+ 
+"1010" in binary  --> 10
+"12"   in octal   --> 10
+"A"    in hex     --> 10
+"junk" in base-36 --> 926192
+"012"  in auto-detected base --> 10
+"0xA"  in auto-detected base --> 10
+"junk" in auto-detected base --> 0

References

See also

+ + + + +
+
(C99)
 converts a byte string to an integer value
(function)
+
(C99)
 converts a byte string to an unsigned integer value
(function)
+
(C95)(C99)
 converts a wide string to an integer value
(function)
+
(C95)(C99)
 converts a wide string to an unsigned integer value
(function)
C++ documentation for strtol, strtoll
+

+ © cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
+ https://en.cppreference.com/w/c/string/byte/strtol +

+
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