READ(2) System Calls Manual READ(2)NAME
read - read from file
SYNOPSIS
read(fildes, buffer, nbytes)
char *buffer;
DESCRIPTION
A file descriptor is a word returned from a successful open, creat, dup, or pipe call. Buffer is the location of nbytes contiguous bytes
into which the input will be placed. It is not guaranteed that all nbytes bytes will be read; for example if the file refers to a type-
writer at most one line will be returned. In any event the number of characters read is returned.
If the returned value is 0, then end-of-file has been reached.
SEE ALSO open(2), creat(2), dup(2), pipe(2)DIAGNOSTICS
As mentioned, 0 is returned when the end of the file has been reached. If the read was otherwise unsuccessful the return value is -1.
Many conditions can generate an error: physical I/O errors, bad buffer address, preposterous nbytes, file descriptor not that of an input
file.
ASSEMBLER
(read = 3.)
(file descriptor in r0)
sys read; buffer; nbytes
(byte count in r0)
READ(2)
Check Out this Related Man Page
dup(2) System Calls Manual dup(2)NAME
dup - duplicate an open file descriptor
SYNOPSIS DESCRIPTION
fildes is a file descriptor obtained from a or system call. returns a new file descriptor having the following in common with the origi-
nal:
o Same open file (or pipe).
o Same file pointer (i.e., both file descriptors share one file pointer).
o Same access mode (read, write or read/write).
o Same file status flags (see fcntl(2),
The new file descriptor is set to remain open across system calls. See fcntl(2).
The file descriptor returned is the lowest one available.
RETURN VALUE
Upon successful completion, the file descriptor is returned as a non-negative integer. Otherwise, a value of -1 is returned and is set to
indicate the error.
ERRORS
fails if one or more of the following is true:
fildes is not a valid open file descriptor.
Request violates the maximum number of open file descriptors.
AUTHOR
was developed by AT&T and HP.
SEE ALSO close(2), creat(2), dup2(2), exec(2), fcntl(2), open(2), pipe(2), privileges(5).
STANDARDS CONFORMANCE dup(2)
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