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UNIX PROGRAMMER'S MANUAL
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Fourth Edition
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K. Thompson
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D. M. Ritchie
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November, 1973
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Copyright \(co 1972, 1973
Bell Telephone Laboratories, Inc.
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No part of this document may be reproduced,
or distributed outside the Laboratories, without
the written permission of Bell Telephone Laboratories.
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Copyright \(co 1972, 1973
Bell Telephone Laboratories, Incorporated
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This manual was set
by a Graphic Systems phototypesetter driven
by the \fItroff\fR formatting program operating
under the \s8UNIX\s10 system.
The text of the manual was
prepared using the \fIed\fR text editor.
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PREFACE
to the Fourth Edition
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In the months since the last appearance of this manual,
many changes have occurred
both in the system itself and in the way it is
used.
The most important changes result from a complete
rewrite of the \s8UNIX\s10 system in the C language.
There have also been substantial changes in much of the
system software.
It is these changes, of course,
which mandated the new edition of this manual.
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The number of \s8UNIX\s10 installations
is now above 20, and many more are expected.
None of these has exactly the same complement
of hardware or software.
Therefore, at any particular installation,
it is quite possible that this manual will
give inappropriate information.
In particular,
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the information in this manual applies
only to \s8UNIX\s10 systems which operate
under the C language versions of the system.
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Installations which use older versions of \s8UNIX\s10
will find earlier editions of this manual
more appropriate to their situation.
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Even in installations which have the latest versions of the
operating system,
not all the software and other
facilities mentioned herein
will be available.
For example,
the typesetter, voice response unit, and voice synthesizer
are hardly universally available devices;
also, some of the \s8UNIX\s10 software has not been
released for use outside the
Bell System.
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The authors are grateful
to L. L. Cherry,
M. E. Lesk,
E. N. Pinson,
and C. S. Roberts for their
contributions
to the system software,
and to L. E. McMahon for software and for
his contributions to this manual.
We are particularly appreciative of the
invaluable technical, editorial, and administrative
efforts of
J. F. Ossanna, M. D. McIlroy, and R. Morris.
They all contributed greatly to the stock of
\s8UNIX\s10 software and to this manual.
Their inventiveness,
thoughtful criticism,
and ungrudging support
increased immeasurably
not only whatever success the \s8UNIX\s10 system enjoys,
but also our own enjoyment in its creation.
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INTRODUCTION TO THIS MANUAL
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This manual gives descriptions of the publicly available
features of \s8UNIX\s10.
It provides neither a general
overview (see ``The \s8UNIX\s10 Time-sharing System'' for that)
nor details of the implementation of the system (which
remain to be disclosed).
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Within the area it surveys, this manual attempts
to be as complete and timely as possible.
A conscious
decision was made to describe each program
in exactly the state it was in at the time
its manual section
was prepared.
In particular, the
desire to describe something as it should be, not as it is,
was resisted.
Inevitably, this means that
many sections will soon be out of date.
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This manual is divided into
eight sections:
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.nf
	I.	Commands
	II.	System calls
	III.	Subroutines
	IV.	Special files
	V.	File formats
	VI.	User-maintained programs
	VII.	Miscellaneous
	VIII.	Maintenance
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.fi
Commands are programs intended to be invoked directly by
the user, in contradistinction to subroutines, which are
intended to be called by the user's programs.
Commands generally reside in directory
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/bin
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(for \fIbin\fR\|ary programs).
This directory is searched automatically
by the command line interpreter.
Some programs also reside in
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/\|usr/\|bin,
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to save space in
\fI/bin.\fR
Some programs
classified as commands are located elsewhere; this
fact is indicated in the appropriate sections.
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System calls are entries into the \s8UNIX\s10 supervisor.
In assembly language, they are coded with the use
of the opcode \fIsys\fR, a synonym for the
\fItrap\fR instruction.
In this edition,
the C language interface routines to the system
calls have been incorporated in section II.
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A small assortment
of subroutines is available;
they are described in section III.
The binary form of most of them is kept in
the system library
\fI/\|lib/\|liba.a.\fR
The subroutines available from C and from Fortran are also included;
they reside in
\fI/\|lib/\|libc.a\fR
and
\fI/\|lib/\|libf.a\fR
respectively.
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The special files section IV discusses the characteristics of
each system ``file'' which actually refers to an I/O device.
The names in this
section refer to the DEC device names for the
hardware,
instead of the names of
the special files themselves.
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The file formats section V documents the structure of particular
kinds of files; for example, the form of the output of the loader and
assembler is given.  Excluded are files used by only one command,
for example the assembler's intermediate files.
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User-maintained programs (section VI) are not considered part
of the \s8UNIX\s10 system, and the principal reason for
listing them is to indicate their existence without
necessarily giving a complete description.
The author should be consulted for information.
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The miscellaneous section (VII) gathers odds and ends.
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Section VIII discusses commands which are not intended
for use by the ordinary user,
in some cases because they disclose information
in which he is presumably not interested,
and in others because they perform
privileged functions.
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Each section consists of a number of independent
entries of a page or so each.
The name of the entry is in the upper corners of its pages,
its preparation date in the upper middle.
Entries within each section are
alphabetized.
The page numbers of each entry start at 1.
(The earlier hope for frequent, partial
updates of the manual is clearly in vain, but
in any event it is not feasible to
maintain consecutive page numbering in a document
like this.)
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All entries are based on a common format,
not all of whose subsections will always appear.
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The \fIname\fR section repeats the entry name and gives
a very short description of its purpose.
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The \fIsynopsis\fR summarizes the use of the
program being described.
A few conventions are used, particularly in the
Commands section:
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\fBBoldface\fR words are considered literals, and
are typed just as they appear.
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Square brackets ( [ ] ) around an argument
indicate that the argument is optional.
When an argument is given as ``name'', it always
refers to a file name.
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Ellipses ``.\|.\|.'' are used to show that the previous argument-prototype
may be repeated.
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A final convention is used by the commands themselves.
An argument beginning with a minus sign ``_''
is often taken to mean some sort of flag argument
even if it appears in a position where a file name
could appear.  Therefore, it is unwise to have files
whose names begin with ``_''.
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The \fIdescription\fR section discusses in detail the subject at hand.
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The \fIfiles\fR section gives the names of files which are
built into the program.
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A
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see also
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section gives pointers to related information.
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A \fIdiagnostics\fR
section discusses
the diagnostic indications which may be produced.
Messages which are intended to be self-explanatory
are not listed.
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The \fIbugs\fR section gives
known bugs and sometimes deficiencies.
Occasionally also the suggested fix is
described.
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.in 0
At the beginning of this document is a table of contents,
organized by section and alphabetically within each section.
There is also a permuted index derived from the table of contents.
Within each index entry, the title
of the writeup to which
it refers is followed by the appropriate section number in parentheses.
This fact is important because there is considerable
name duplication among the sections,
arising principally from commands which
exist only to exercise a particular system call.
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This manual was prepared using the \s8UNIX\s10 text
editor \fIed\fR and the formatting program \fItroff\fR.