.na .bl 15 .tr | .in 0 .ce UNIX PROGRAMMER'S MANUAL .ce Third Edition .ce 3 K. Thompson D. M. Ritchie .ce February, 1973 .sp 15 .ce 7 Copyright 8c9 1972 Bell Telephone Laboratories, Inc. No part of this document may be reproduced, or distributed outside the Laboratories, without the written permission of Bell Telephone Laboratories. .bp .fo ''- % -'' .ro .bl 2 .ce 2 PREFACE to the Third Edition 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. Perhaps most obviously, there have been additions, deletions, and modifications to the system and its software. It is these changes, of course, that caused the appearance of this revised manual. Second, the number of people spending an appreciable amount of time writing UNIX software has increased. Credit is due to L.|L.|Cherry, M.|D.|McIlroy, L.|E.|McMahon, R.|Morris, J.|F.|Ossanna, and E.|N.|Pinson for their contributions. Finally, the number of UNIX installations has grown to 16, with more 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. .a In particular, .ul 3 any system which uses a PDP-11/20 processor will not include all the software described herein, nor will the software behave the same way. The second, or even the first, edition of this manual is likely to be more appropriate. Besides additions, deletions, and modifications to the writeups in each section, this manual differs from its predecessors in two ways: all the commands used for system maintenance and not intended for normal users have been moved to a new section VIII; and there is a new "How to Get Started" chapter that gives some elementary facts and many pointers to other sections. .bp .bl 2 .ce INTRODUCTION TO THIS MANUAL This manual gives descriptions of the publicly available features of UNIX. It provides neither a general overview (see "The UNIX Time-sharing System" for that) nor details of the implementation of the system (which remain to be disclosed). 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. (The rate of change of the system is so great that a dismayingly large number of early sections had to be modified while the rest were being written. The unbounded effort required to stay up-to-date is best indicated by the fact that several of the programs described were written specifically to aid in preparation of this manual!) This manual is divided into eight sections: I. Commands II. System calls III. Subroutines IV. Special files V. File formats VI. User-maintained programs VII. Miscellaneous VIII. Maintenance 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 /bin____ (for bin___ary programs). This directory is searched automatically by the command line interpreter. Some programs classified as commands are located elsewhere; this fact is indicated in the appropriate sections. System calls are entries into the UNIX supervisor. In assembly language, they are coded with the use of the opcode "sys", a synonym for the trap____ instruction. 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 /usr/lib/liba.a. The special files section IV discusses the characteristics of each system "file" which actually refers to an I/O device. Unlike previous editions, the names in this section refer to the DEC device names for the hardware, instead of the neames of the special files themselves. 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. User-maintained programs (section VI) are not considered part of the UNIX 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. The miscellaneous section (VII) gathers odds and ends. 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. 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.) All entries have a common format. .sp .in 5 The name____ section repeats the entry name and gives a very short description of its purpose. The synopsis________ summarizes the use of the program being described. A few conventions are used, particularly in the Commands section: .in 8 Underlined words are considered literals, and are typed just as they appear. 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. Ellipses "..." are used to show that the previous argument-prototype may be repeated. 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 "-". .in 5 The description___________ section discusses in detail the subject at hand. The files_____ section gives the names of files which are built into the program. A see___ also____ section gives pointers to related information. A diagnostics___________ section discusses the diagnostics that may be produced. This section tends to be as terse as the diagnostics themselves. The bugs____ section gives known bugs and sometimes deficiencies. Occasionally also the suggested fix is described. .in 0 Previous edition of this manual had an owner_____ section, which has been dropped from this edition because the "owners" of many routines became fairly hard to pin down. The major contributors to UNIX, (cast in order of appearance) together with their login names and most notable contributions, are ken K. Thompson (UNIX, many commands) dmr D. M. Ritchie (many commands, as, ld, C) jfo J. F. Ossanna (roff, nroff) doug M. D. McIlroy (tmg, m6) rhm R. Morris (dc, much of library) lem L. E. McMahon (cref) llc L. L. Cherry (form, fed, salloc) csr C. S. Roberts (tss) enp E. N. Pinson (proof) 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. This manual was prepared using the UNIX text editor ed__ and the formatting program roff____. The assistance of R. Morris is gratefully acknowledged.