| /**************************************************************************** |
| | (C) Copyright 2008 Novell, Inc. All Rights Reserved. |
| | |
| | GPLv2: This program is free software; you can redistribute it |
| | and/or modify it under the terms of version 2 of the GNU General |
| | Public License as published by the Free Software Foundation. |
| | |
| | This program is distributed in the hope that it will be useful, |
| | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| | GNU General Public License for more details. |
| +-------------------------------------------------------------------------*/ |
| |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| #include <fcntl.h> |
| #include <unistd.h> |
| #include <stdlib.h> |
| #include <stdio.h> |
| |
| /* |
| * WRITE(2) Linux Programmer's Manual WRITE(2) |
| * |
| * |
| * |
| * NAME |
| * write - write to a file descriptor |
| * |
| * SYNOPSIS |
| * #include <unistd.h> |
| * |
| * ssize_t write(int fd, const void *buf, size_t count); |
| * |
| * DESCRIPTION |
| * write() writes up to count bytes from the buffer pointed buf to the |
| * file referred to by the file descriptor fd. |
| * |
| * The number of bytes written may be less than count if, for example, |
| * there is insufficient space on the underlying physical medium, or the |
| * RLIMIT_FSIZE resource limit is encountered (see setrlimit(2)), or the |
| * call was interrupted by a signal handler after having written less |
| * than count bytes. (See also pipe(7).) |
| * |
| * For a seekable file (i.e., one to which lseek(2) may be applied, for |
| * example, a regular file) writing takes place at the current file off- |
| * set, and the file offset is incremented by the number of bytes actu- |
| * ally written. If the file was open(2)ed with O_APPEND, the file off- |
| * set is first set to the end of the file before writing. The adjust- |
| * ment of the file offset and the write operation are performed as an |
| * atomic step. |
| * |
| * POSIX requires that a read(2) which can be proved to occur after a |
| * write() has returned returns the new data. Note that not all file |
| * systems are POSIX conforming. |
| * |
| * RETURN VALUE |
| * On success, the number of bytes written is returned (zero indicates |
| * nothing was written). On error, -1 is returned, and errno is set |
| * appropriately. |
| * |
| * If count is zero and fd refers to a regular file, then write() may |
| * return a failure status if one of the errors below is detected. If no |
| * errors are detected, 0 will be returned without causing any other |
| * effect. If count is zero and fd refers to a file other than a regular |
| * file, the results are not specified. |
| * |
| * ERRORS |
| * EAGAIN The file descriptor fd has been marked non-blocking (O_NON- |
| * BLOCK) and the write would block. |
| * |
| * EBADF fd is not a valid file descriptor or is not open for writing. |
| * |
| * EFAULT buf is outside your accessible address space. |
| * |
| * EFBIG An attempt was made to write a file that exceeds the implemen- |
| * tation-defined maximum file size or the process's file size |
| * limit, or to write at a position past the maximum allowed off- |
| * set. |
| * |
| * EINTR The call was interrupted by a signal before any data was writ- |
| * ten; see signal(7). |
| * |
| * EINVAL fd is attached to an object which is unsuitable for writing; or |
| * the file was opened with the O_DIRECT flag, and either the |
| * address specified in buf, the value specified in count, or the |
| * current file offset is not suitably aligned. |
| * |
| * EIO A low-level I/O error occurred while modifying the inode. |
| * |
| * ENOSPC The device containing the file referred to by fd has no room |
| * for the data. |
| * |
| * EPIPE fd is connected to a pipe or socket whose reading end is |
| * closed. When this happens the writing process will also |
| * receive a SIGPIPE signal. (Thus, the write return value is |
| * seen only if the program catches, blocks or ignores this sig- |
| * nal.) |
| * |
| * Other errors may occur, depending on the object connected to fd. |
| * |
| * CONFORMING TO |
| * SVr4, 4.3BSD, POSIX.1-2001. |
| * |
| * Under SVr4 a write may be interrupted and return EINTR at any point, |
| * not just before any data is written. |
| * |
| * NOTES |
| * A successful return from write() does not make any guarantee that data |
| * has been committed to disk. In fact, on some buggy implementations, |
| * it does not even guarantee that space has successfully been reserved |
| * for the data. The only way to be sure is to call fsync(2) after you |
| * are done writing all your data. |
| * |
| * If a write() is interrupted by a signal handler before any bytes are |
| * written, then the call fails with the error EINTR; if it is inter- |
| * rupted after at least one byte has been written, the call succeeds, |
| * and returns the number of bytes written. |
| * |
| * SEE ALSO |
| * close(2), fcntl(2), fsync(2), ioctl(2), lseek(2), open(2), pwrite(2), |
| * read(2), select(2), writev(2), fwrite(3) |
| * |
| * COLOPHON |
| * This page is part of release 3.13 of the Linux man-pages project. A |
| * description of the project, and information about reporting bugs, can |
| * be found at http://www.kernel.org/doc/man-pages/. |
| * |
| * |
| * |
| * Linux 2007-06-18 WRITE(2) |
| */ |
| |
| enum { MAX_BUF = 1 }; |
| char Buf[MAX_BUF] = { 'a' }; |
| |
| int main (int argc, char *argv[]) |
| { |
| char *name; |
| int fd; |
| int rc; |
| |
| if (argc > 1) { |
| name = argv[1]; |
| } else { |
| name = "/mnt/tau/xyzzy"; |
| } |
| |
| fd = creat(name, 0666); |
| if (fd == -1) { |
| perror(name); |
| exit(1); |
| } |
| rc = write(fd, Buf, sizeof(Buf)); |
| if (rc == -1) { |
| perror(name); |
| exit(1); |
| } |
| if (rc != sizeof(Buf)) { |
| fprintf(stderr, "Asked to write %zu bytes but only wrote %d bytes\n", |
| sizeof(Buf), rc); |
| exit(1); |
| } |
| close(fd); |
| return 0; |
| } |
