C-style file input/output --- unformatted input/output --- (std::fputc, std::putc, std::fputs)

The CI/O subset of the C++ standard library implements C-style stream input/output operations. The <cstdio> header file provides general file support and provides functions with narrow and multibyte character input/output capabilities, while the <cwchar> header file provides functions with wide character input/output capabilities.

Unformatted input/output

Write characters to file stream

std::fputc, 
std::putc

int fputc( int ch, std::FILE* stream ); int putc( int ch, std::FILE* stream );

Write characters chto the given output stream stream.

Internally, characters are converted to unsigned char before writing.

In C, putc() can be implemented as a macro, which is prohibited in C++. Thus calling std::fputc() and std::putc() always have the same effect.

parameter

ch	-	characters to write
stream	-	output stream

return value

On success, returns the character written.

On failure, returns EOF and sets the error indicator on the stream (see std::ferror()).

Call example

#include <cstdio>

int main()
{
    for (char c = 'a'; c != 'z'; c++)
    {
        std::putc(c, stdout);
    }
    std::putc('\n', stdout);

    // putchar 的返回值不等于参数
    int r = 0x1070;
    std::printf("\n0x%x\n", r);
    r = std::putchar(r);
    std::printf("\n0x%x\n", r);
    return 0;
}

output

Write string to file stream

std::fputs

int fputs( const char* str, std::FILE* stream );

Write streach character from the null-terminated string to stream, as by repeatedly executing std::fputc.

strThe terminating null character from is not written .

parameter

str	-	null terminated string to write
stream	-	output stream

return value

On success, returns a non-negative value.

On failure, returns EOF and sets the errorstream indicator on (see std::ferror).

Notice

The related function std::puts appends a newline character to the output and std::fputswrites an unmodified string.

Different implementations return different non-negative numbers: some return the last character written, some return the number of characters written (or this value if the string is longer than INT_MAX), some simply a non-negative constant, such as zero.

Call example

#include <cstdio>

int main(void)
{
    int rc = std::fputs("Hello World", stdout);

    if (rc == EOF)
    {
        std::perror("fputs()");    // POSIX 要求设置 errno
    }
    return 0;
}

output