Difference between revisions of "c/string/byte/strstr"
From cppreference.com
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|code= | |code= | ||
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#include <stdio.h> | #include <stdio.h> | ||
| + | #include <string.h> | ||
void find_str(char const *str, char const *substr) | void find_str(char const *str, char const *substr) | ||
{ | { | ||
| − | char *pos = strstr(str, substr); | + | char const *pos = strstr(str, substr); |
| − | pos | + | if (pos) |
| − | + | printf( | |
| − | + | "found the string '%s' in '%s' at position %td\n", | |
| − | + | substr, str, pos - str | |
| + | ); | ||
| + | else | ||
| + | printf( | ||
| + | "the string '%s' was not found in '%s'\n", | ||
| + | substr, str | ||
| + | ); | ||
} | } | ||
int main(void) | int main(void) | ||
{ | { | ||
| − | char *str = "one two three"; | + | char const *str = "one two three"; |
find_str(str, "two"); | find_str(str, "two"); | ||
find_str(str, ""); | find_str(str, ""); | ||
Revision as of 01:42, 1 October 2024
| Defined in header <string.h>
|
||
| char *strstr( const char *str, const char *substr ); |
(1) | |
| /*QChar*/ *strstr( /*QChar*/ *str, const char *substr ); |
(2) | (since C23) |
1) Finds the first occurrence of the null-terminated byte string pointed to by
substr in the null-terminated byte string pointed to by str. The terminating null characters are not compared.2) Type-generic function equivalent to (1). Let
T be an unqualified character object type.
- If
stris of type const T*, the return type is const char*. - Otherwise, if
stris of type T*, the return type is char*. - Otherwise, the behavior is undefined.
- If
The behavior is undefined if either str or substr is not a pointer to a null-terminated byte string.
Contents |
Parameters
| str | - | pointer to the null-terminated byte string to examine |
| substr | - | pointer to the null-terminated byte string to search for |
Return value
Pointer to the first character of the found substring in str, or a null pointer if such substring is not found. If substr points to an empty string, str is returned.
Example
Run this code
#include <stdio.h> #include <string.h> void find_str(char const *str, char const *substr) { char const *pos = strstr(str, substr); if (pos) printf( "found the string '%s' in '%s' at position %td\n", substr, str, pos - str ); else printf( "the string '%s' was not found in '%s'\n", substr, str ); } int main(void) { char const *str = "one two three"; find_str(str, "two"); find_str(str, ""); find_str(str, "nine"); find_str(str, "n"); return 0; }
Output:
found the string 'two' in 'one two three' at position 4 found the string '' in 'one two three' at position 0 the string 'nine' was not found in 'one two three' found the string 'n' in 'one two three' at position 1
References
- C17 standard (ISO/IEC 9899:2018):
- 7.24.5.7 The strstr function (p: 269)
- C11 standard (ISO/IEC 9899:2011):
- 7.24.5.7 The strstr function (p: 369)
- C99 standard (ISO/IEC 9899:1999):
- 7.21.5.7 The strstr function (p: 332)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.11.5.7 The strstr function
See also
| finds the first occurrence of a character (function) | |
| finds the last occurrence of a character (function) | |
| C++ documentation for strstr
| |
