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alarm—Sets an alarm clock for delivery of a signal
SYNOPSIS
#include <unistd.h> unsigned int alarm(unsigned int seconds);
DESCRIPTION
alarm arranges for a SIGALRM signal to be delivered to the process in seconds seconds.
If seconds is 0, no new alarm is scheduled.
In any event, any previously set alarm is canceled.
RETURN VALUE
alarm returns the number of seconds remaining until any previously scheduled alarm was due to be delivered, or 0 if there was no previously scheduled alarm.
NOTES
alarm and setitimer share the same timer; calls to one will interfere with use of the other.
Scheduling delays can, as ever, cause the execution of the process to be delayed by an arbitrary amount of time.
CONFORMS TO
SVID, AT&T, POSIX, X/OPEN, BSD 4.3
SEE ALSO
setitimer(2), signal(2), sigaction(2), gettimeofday(2), select(2), pause(2), sleep(3)
Linux, 21 July 1993
bdflush—Starts, flushes, or tunes the buffer-dirty-flush daemon
SYNOPSIS
int bdflush(int func, long *address); int bdflush(int func, long data);
DESCRIPTION
bdflush starts, flushes, or tunes the buffer-dirty-flush daemon. Only the superuser may call bdflush.
If func is negative or 0 and no daemon has been started, bdflush enters the daemon code and never returns.
If func is 1, some dirty buffers are written to disk.
If func is 2 or more and is even (low bit is 0), address is the address of a long word, and the tuning parameter numbered (func_2)/2 is returned to the caller in that address.
If func is 3 or more and is odd (low bit is 1), data is a long word and the kernel sets tuning parameter numbered (func_3)/2 to that value.
The set of parameters, their values, and their legal ranges are defined in the kernel source file fs/buffer.c.
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RETURN VALUE
If func is negative or 0 and the daemon successfully starts, bdflush never returns. Otherwise, the return value is 0 on success and _1 on failure, with errno set to indicate the error.
ERRORS
| EPERM | Caller is not superuser. |
| EFAULT | address points outside your accessible address space. |
| EBUSY | An attempt was made to enter the daemon code after another process has already been entered. |
| EINVAL | An attempt was made to read or write an invalid parameter number, or to write an invalid value to a parameter. |
SEE ALSO
fsync(2), sync(2), update(8), sync(8)
Linux 1.2.4, 15 April 1995
bind—Binds a name to a socket
SYNOPSIS
#include <sys/types.h> #include <sys/socket.h> int bind(int sockfd, struct sockaddr *my_addr,intaddrlen);
DESCRIPTION
bind gives the socket, sockfd, the local address my_addr. my_addr is addrlen bytes long. Traditionally, this is called assigning a name to a socket. (When a socket is created with socket(2), it exists in a name space—an address family—but has no name assigned.)
NOTES
Binding a name in the UNIX domain creates a socket in the file system that must be deleted by the caller—using
unlink(2)
—when it is no longer needed.
The rules used in name binding vary between communication domains. Consult the manual entries in section 4 for detailed information.
RETURN VALUE
On success, 0 is returned. On error, _1 is returned, and errno is set appropriately.
ERRORS
| EBADF | sockfd is not a valid descriptor. |
| EINVAL | The socket is already bound to an address. This may change in the future. See linux/unix/sock.c for details. |
| EACCES | The address is protected and the user is not the superuser. |
The following errors are specific to UNIX domain (AF_UNIX) sockets:
| EINVAL | addr len was wrong, or the socket was not in the AF_UNIX family. |
| EROFS | The socket inode would reside on a read-only file system. |
| EFAULT | my_addr points outside your accessible address space. |
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| ENAMETOOLONG | my_addr is too long. |
| ENOENT | The file does not exist. |
| ENOMEM | Insufficient kernel memory was available. |
| ENOTDIR | A component of the path prefix is not a directory. |
| EACCES | Search permission is denied on a component of the path prefix. |
| ELOOP | my_addr contains a circular reference (that is, via a symbolic link). |
HISTORY
The bind function call appeared in BSD 4.2.
SEE ALSO
accept(2), connect(2), listen(2), socket(2), getsockname(2)
Linux 0.99.11, 23 July 1993
brk, sbrk—Change data segment size
SYNOPSIS
#include <unistd.h> int brk(void *end_data_segment); void *sbrk(ptrdiff tincrement);
DESCRIPTION
brk sets the end of the data segment to the value specified by end_data_segment.
end_data_segment must be greater than the end of the text segment and it must be 16KB before the end of the stack.
sbrk increments the program's data space by increment bytes. sbrk isn't a system call; it is just a C library wrapper.
RETURN VALUE
On success, brk returns 0, and sbrk returns a pointer to the start of the new area. On error, _1 is returned and errno is set to ENOMEM.
CONFORMS TO
BSD 4.3
brk and sbrk are not defined in the C standard and are deliberately excluded from the POSIX.1 standard (see paragraphs B.1.1.1.3 and B.8.3.3).
SEE ALSO
execve(2), getrlimit(2), malloc(3), end(3)
Linux 0.99.11, 21 July 1993
cacheflush—Flushes contents of the instruction and/or data cache
SYNOPSIS