stdin, stdout, stderr
From cppreference.com
Defined in header <stdio.h>
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#define stdin /* implementation-defined */ |
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#define stdout /* implementation-defined */ |
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#define stderr /* implementation-defined */ |
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Three text streams are predefined. These streams are implicitly opened and unoriented at program startup.
1) Associated with the standard input
2) Associated with the standard output
3) Associated with the standard error stream, used for writing diagnostic output. At program startup, the stream is not fully buffered.
What constitutes an interactive device is implementation-defined.
These macros are expanded to expressions of type FILE*.
Notes
Although not mandated by POSIX, the UNIX convention is that stdin and stdout are line-buffered if associated with a terminal and stderr is unbuffered.
These macros may be expanded to modifiable lvalues. If any of these FILE*
Example
This example shows a function equivalent to printf.
Run this code
#include <stdarg.h> #include <stdio.h> int my_printf(const char* restrict fmt, ...) { va_list vl; va_start(vl, fmt); int ret = vfprintf(stdout, fmt, vl); va_end(vl); return ret; } int main(void) { my_printf("Rounding:\t%f %.0f %.32f\n", 1.5, 1.5, 1.3); my_printf("Padding:\t%05.2f %.2f %5.2f\n", 1.5, 1.5, 1.5); my_printf("Scientific:\t%E %e\n", 1.5, 1.5); my_printf("Hexadecimal:\t%a %A\n", 1.5, 1.5); }
Possible output:
Rounding: 1.500000 2 1.30000000000000004440892098500626 Padding: 01.50 1.50 1.50 Scientific: 1.500000E+00 1.500000e+00 Hexadecimal: 0x1.8p+0 0X1.8P+0
References
- C23 standard (ISO/IEC 9899:2024):
- 7.21.1 Introduction (p: TBD)
- 7.21.2 Streams (p: TBD)
- 7.21.2 Files (p: TBD)
- C17 standard (ISO/IEC 9899:2018):
- 7.21.1 Introduction (p: 217-218)
- 7.21.2 Streams (p: 217-219)
- 7.21.2 Files (p: 219-221)
- C11 standard (ISO/IEC 9899:2011):
- 7.21.1 Introduction (p: 296-298)
- 7.21.2 Streams (p: 298-299)
- 7.21.2 Files (p: 300-302)
- C99 standard (ISO/IEC 9899:1999):
- 7.19.1 Introduction (p: 262-264)
- 7.19.2 Streams (p: 264-265)
- 7.19.2 Files (p: 266-268)
- C89/C90 standard (ISO/IEC 9899:1990):
- 7.9.1 Introduction
- 7.9.2 Streams
- 7.9.3 Files
See also
| object type, capable of holding all information needed to control a C I/O stream (typedef) |
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C++ documentation for stdin, stdout, stderr
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