119 lines
2.3 KiB
Groff
119 lines
2.3 KiB
Groff
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READ(2) Minix Programmer's Manual READ(2)
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NAME
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read - read input
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SYNOPSIS
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#include <sys/types.h>
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#include <unistd.h>
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ssize_t read(int d, void *buf, size_t nbytes)
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DESCRIPTION
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Read attempts to read nbytes of data from the object referenced by the
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descriptor d into the buffer pointed to by buf.
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On objects capable of seeking, the read starts at a position given by the
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pointer associated with d (see lseek(2)). Upon return from read, the
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pointer is incremented by the number of bytes actually read.
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Objects that are not capable of seeking always read from the current
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position. The value of the pointer associated with such an object is
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undefined.
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Upon successful completion, read return the number of bytes actually read
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and placed in the buffer. The system guarantees to read the number of
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bytes requested if the descriptor references a normal file that has that
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many bytes left before the end-of-file, but in no other case.
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If the returned value is 0, then end-of-file has been reached.
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RETURN VALUE
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If successful, the number of bytes actually read is returned. Otherwise,
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a -1 is returned and the global variable errno is set to indicate the
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error.
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ERRORS
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Read will fail if one or more of the following are true:
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[EBADF] D is not a valid descriptor open for reading.
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[EFAULT] Buf points outside the allocated address space.
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[EIO] An I/O error occurred while reading from the file system.
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[EINTR] A read from a slow device was interrupted before any data
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arrived by the delivery of a signal.
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[EAGAIN] The file was marked for non-blocking I/O, and no data were
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ready to be read.
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4BSD May 23, 1986 1
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READ(2) Minix Programmer's Manual READ(2)
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SEE ALSO
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dup(2), fcntl(2), open(2), pipe(2), write(2).
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4BSD May 23, 1986 2
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