fix worst-case buffer sizes for non-blocking I/O

[unix-history] / usr / src / bin / cat / cat.1

.\" Copyright (c) 1989, 1990 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the Institute of Electrical and Electronics Engineers, Inc.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)cat.1	6.16 (Berkeley) %G%
.\"
.Dd 
.Dt CAT 1
.Os BSD 3
.Sh NAME
.Nm cat
.Nd concatenate and print files
.Sh SYNOPSIS
.Nm cat
.Op Fl benstuv
.Op Fl
.Op Ar
.Sh DESCRIPTION
The
.Nm cat
utility reads files sequentially, writing them to the standard output.
The
.Ar file
operands are processed in command line order.
A single dash represents standard input.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl b
Implies the
.Fl n
option but doesn't number blank lines.
.It Fl e
Implies the
.Fl v
option, and displays a dollar sign
.Pq Ql \&$
at the end of each line
as well.
.It Fl n
Number the
.Ar output
lines, starting at 1.
.It Fl s
Squeeze multiple adjacent empty lines, causing the output to be
single spaced.
.It Fl t
Implies the
.Fl v
option, and displays tab characters as
.Pq Ql ^I
as well.
.It Fl u
The
.Fl u
option guarantees that the output is unbuffered.
.It Fl v
Displays non-printing characters so they are visible.
Control characters print line
.Ql ^X
for control-X; the delete
character (octal 0177) prints as
.Ql ^?
Non-ascii characters (with the high bit set) are printed as
.Ql M-
(for meta) followed by the character for the low 7 bits.
.El
.Pp
The
.Nm cat
utility exits 0 on success, and >0 if an error occurs.
.Sh BUGS
Because of the shell language mechanism used to perform output
redirection, the command
.Dq Li cat file1 file 2 > file1
will cause the original data in file1 to be destroyed!
.Sh SEE ALSO
.Xr head 1 ,
.Xr more 1 ,
.Xr pr 1 ,
.Xr tail 1
.Rs
.%A Rob Pike
.%T "UNIX Style, or cat -v Considered Harmful"
.%J "USENIX Summer Conference Proceedings"
.%D 1983
.Re
.Sh HISTORY
A
.Nm
command appeared in Version 6 AT&T UNIX.