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Difference between revisions of "cpp/io/c/rewind"

From cppreference.com
< cpp‎ | io‎ | c
m (Text replace - "{{cpp|" to "{{c|")
m (linked the `ungetc`)
 
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{{cpp/title | rewind }}
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{{cpp/title|rewind }}
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{{cpp/io/c/sidebar}}
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{{cpp/io/c/navbar}}
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{{ddcl | header=cstdio |
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{{ddcl|header=cstdio|
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void rewind( FILE *stream );
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void rewind( std::FILE* stream );
 
}}
 
}}
  
−
Moves the file position indicator to the beginning of the given file stream. {{c|EOF}} and error flags are also cleared.  
+
Moves the file position indicator to the beginning of the given file stream.
 +
 
 +
The function is equivalent to {{c|std::fseek(stream, 0, SEEK_SET);}}, except that end-of-file and error indicators are cleared.
 +
 
 +
The function drops any effects from previous calls to {{lc|std::ungetc|ungetc}}.
  
 
===Parameters===
 
===Parameters===
−
{{param list begin}}
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{{par begin}}
−
{{param list item | stream | file stream to modify}}
+
{{par|stream|file stream to modify}}
−
{{param list end}}
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{{par end}}
  
 
===Return value===
 
===Return value===
 
(none)
 
(none)
 +
 +
===Example===
 +
{{example|
 +
|code=
 +
#include <array>
 +
#include <cstdio>
 +
 +
int main()
 +
{
 +
    std::FILE* f = std::fopen("file.txt", "w");
 +
    for (char ch = '0'; ch <= '9'; ch++)
 +
        std::fputc(ch, f);
 +
    std::fclose(f);
 +
 +
    std::array<char, 20> str;
 +
    std::FILE* f2 = std::fopen("file.txt", "r");
 +
 +
    const unsigned size1 = std::fread(str.data(), 1, str.size(), f2);
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    std::puts(str.data());
 +
    std::printf("size1 = %u\n", size1);
 +
 +
    std::rewind(f2);
 +
 +
    const unsigned size2 = std::fread(str.data(), 1, str.size(), f2);
 +
    std::puts(str.data());
 +
    std::printf("size2 = %u", size2);
 +
 +
    std::fclose(f2);
 +
}
 +
|output=
 +
0123456789
 +
size1 = 10
 +
0123456789
 +
size2 = 10
 +
}}
  
 
===See also===
 
===See also===
−
{{dcl list begin}}
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{{dsc begin}}
−
{{dcl list template | cpp/io/c/dcl list fseek}}
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{{dsc inc|cpp/io/c/dsc fseek}}
−
{{dcl list end}}
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{{dsc see c|c/io/rewind}}
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{{dsc end}}
 +
 
 +
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 09:24, 30 November 2022

 
C++
 
Input/output library
 
C-style I/O
Types and objects
Functions
File access
Direct input/output
Unformatted input/output
Formatted input
(C++11)(C++11)(C++11)    
(C++11)(C++11)(C++11)    
 
Defined in header <cstdio>
void rewind( std::FILE* stream );

Moves the file position indicator to the beginning of the given file stream.

The function is equivalent to std::fseek(stream, 0, SEEK_SET);, except that end-of-file and error indicators are cleared.

The function drops any effects from previous calls to ungetc.

Contents

[edit] Parameters

stream - file stream to modify

[edit] Return value

(none)

[edit] Example

Run this code
#include <array>
#include <cstdio>
 
int main()
{
    std::FILE* f = std::fopen("file.txt", "w");
    for (char ch = '0'; ch <= '9'; ch++)
        std::fputc(ch, f);
    std::fclose(f);
 
    std::array<char, 20> str;
    std::FILE* f2 = std::fopen("file.txt", "r");
 
    const unsigned size1 = std::fread(str.data(), 1, str.size(), f2);
    std::puts(str.data());
    std::printf("size1 = %u\n", size1);
 
    std::rewind(f2);
 
    const unsigned size2 = std::fread(str.data(), 1, str.size(), f2);
    std::puts(str.data());
    std::printf("size2 = %u", size2);
 
    std::fclose(f2);
}

Output: 

0123456789
size1 = 10
0123456789
size2 = 10

[edit] See also

 moves the file position indicator to a specific location in a file
(function) [edit]
C documentation for rewind
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/io/c/rewind&oldid=145312"