FPUTC(3P)

💖 FPUTC(3P) 💖 — the POSIX Programmer's Manual girlie herself

okay so bestie, this is the fputc page from the POSIX Programmer's Manual (that's the <pink>3P</pink> in the title, iykyk) 🫶

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🌸 PROLOG 🌸

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

fr fr, read that again. Linux might do its own thing here, or might not even have it at all. check the Linux page, bestie, don't come for me 😭

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✨ NAME ✨

fputc — put a byte on a stream 🦋

like. one single byte. onto a stream. that's the whole job. iconic behavior honestly.

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🎀 SYNOPSIS 🎀

#include <stdio.h>

int fputc(int c, FILE *stream);

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💅 DESCRIPTION 💅

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.1‐2017 defers to the ISO C standard.

translation: if this page and ISO C ever beef, ISO C wins. not me picking sides, that's just the rules 💜

So here's the tea. The fputc() function shall write the byte specified by c (converted to an unsigned char) to the output stream pointed to by stream, at the position indicated by the associated file-position indicator for the stream (if defined), and shall advance the indicator appropriately. If the file cannot support positioning requests, or if the stream was opened with append mode, the byte shall be appended to the output stream.

The last data modification and last file status change timestamps of the file shall be marked for update between the successful execution of fputc() and the next successful completion of a call to fflush() or fclose() on the same stream or a call to exit() or abort().

so the timestamp glow-up is pending, bestie — it lands somewhere between your successful fputc() and the next fflush(), fclose(), exit() or abort() on that same stream. slay, but on a delay ✨

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🔥 RETURN VALUE 🔥

Upon successful completion, fputc() shall return the value it has written. Otherwise, it shall return EOF, the error indicator for the stream shall be set, and errno shall be set to indicate the error.

so like, it gives you back the byte it wrote. cute. but if it flops? EOF, error indicator set, errno set. three things. not one. THREE. 💀

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🌈 ERRORS 🌈

The fputc() function shall fail if either the stream is unbuffered or the stream's buffer needs to be flushed, and:

• EAGAIN — The O_NONBLOCK flag is set for the file descriptor underlying stream and the thread would be delayed in the write operation.
• EBADF — The file descriptor underlying stream is not a valid file descriptor open for writing.
• EFBIG — An attempt was made to write to a file that exceeds the maximum file size.
• EFBIG — An attempt was made to write to a file that exceeds the file size limit of the process.
• EFBIG — The file is a regular file and an attempt was made to write at or beyond the offset maximum.
• EINTR — The write operation was terminated due to the receipt of a signal, and no data was transferred.
• EIO — A physical I/O error has occurred, or the process is a member of a background process group attempting to write to its controlling terminal, TOSTOP is set, the calling thread is not blocking SIGTTOU, the process is not ignoring SIGTTOU, and the process group of the process is orphaned. This error may also be returned under implementation-defined conditions.
• ENOSPC — There was no free space remaining on the device containing the file.
• EPIPE — An attempt is made to write to a pipe or FIFO that is not open for reading by any process. A SIGPIPE signal shall also be sent to the thread.

bestie, yes, EFBIG really shows up three separate times. three different reasons. that's not a typo, that's just how it is 🍓

The fputc() function may fail if:

• ENOMEM — Insufficient storage space is available.
• ENXIO — A request was made of a nonexistent device, or the request was outside the capabilities of the device.

The following sections are informative.

heads up — informative means it's lore, not law. the real requirements live above ✨

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🧚 EXAMPLES 🧚

None.

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💜 APPLICATION USAGE 💜

None.

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🌸 RATIONALE 🌸

None.

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🦋 FUTURE DIRECTIONS 🦋

None.

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⭐ SEE ALSO ⭐

• Section 2.5, Standard I/O Streams
• ferror()
• fopen()
• getrlimit()
• putc()
• puts()
• setbuf()
• ulimit()
• The Base Definitions volume of POSIX.1‐2017, <stdio.h>

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👑 COPYRIGHT 👑

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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mwah 💋 that's the whole page — brought to you by IEEE/The Open Group, 2017, and the manual name is FPUTC(3P), and if you ever spot a typo it's probably from the man page conversion, not from me, ok bye bestie 🫶✨