stderr, stdin, stdout - standard I/O streams
#include <stdio.h>
extern FILE *stderr, *stdin, *stdout;
[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.A file with associated buffering is called a stream and is declared to be a pointer to a defined type FILE. The fopen() function shall create certain descriptive data for a stream and return a pointer to designate the stream in all further transactions. Normally, there are three open streams with constant pointers declared in the <stdio.h> header and associated with the standard open files.
At program start-up, three streams shall be predefined and need not be opened explicitly: standard input (for reading conventional input), standard output (for writing conventional output), and standard error (for writing diagnostic output). When opened, the standard error stream is not fully buffered; the standard input and standard output streams are fully buffered if and only if the stream can be determined not to refer to an interactive device.
[CX] The following symbolic values in <unistd.h> define the file descriptors that shall be associated with the C-language stdin, stdout, and stderr when the application is started:
- STDIN_FILENO
- Standard input value, stdin. Its value is 0.
- STDOUT_FILENO
- Standard output value, stdout. Its value is 1.
- STDERR_FILENO
- Standard error value, stderr. Its value is 2.
The stderr stream is expected to be open for reading and writing.
None.
No errors are defined.
None.
None.
None.
None.
fclose , feof , ferror , fileno , fopen , fprintf , fread , fscanf , fseek , getc , gets , popen , putc , puts , read , setbuf , setvbuf , tmpfile , ungetc , vfprintf
XBD <stdio.h> , <unistd.h>
First released in Issue 1.
Extensions beyond the ISO C standard are marked.
A note that stderr is expected to be open for reading and writing is added to the DESCRIPTION.
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