std::fopen

std::FILE* fopen( const char* filename, const char* mode );

Opens a file indicated by filename and returns a file stream associated with that file. mode is used to determine the file access mode.

Parameters

Return value

If successful, returns a pointer to the object that controls the opened file stream, with both eof and error bits cleared. The stream is fully buffered unless filename refers to an interactive device.

On error, returns a null pointer. POSIX requires that errno is set in this case.

Notes

The format of filename is implementation-defined, and does not necessarily refer to a file (e.g. it may be the console or another device accessible through filesystem API). On platforms that support them, filename may include absolute or relative filesystem path.

For portable directory and file naming, see C++ filesystem TS or boost.filesystem.

Example

#include <cstdio>
#include <cstdlib>
 
int main()
{
    FILE* fp = std::fopen("test.txt", "r");
    if(!fp) {
        std::perror("File opening failed");
        return EXIT_FAILURE;
    }
 
    int c; // note: int, not char, required to handle EOF
    while ((c = std::fgetc(fp)) != EOF) { // standard C I/O file reading loop
       std::putchar(c);
    }
 
    if (std::ferror(fp))
        std::puts("I/O error when reading");
    else if (std::feof(fp))
        std::puts("End of file reached successfully");
 
    std::fclose(fp);
}

See also