.lg.ll 6i.lt 6i.ps 10.vs 12p.de he.tl '-''''sp .5i'ft R.CH'ft'ps'sp .5i...de fo'ft R'ps 10'sp .5i.CF'ft'ps'bp...wh 0 he.wh -1i fo.de pg.sp .5...tr |.br.sp 3i.ps 18.ft B.ceUNIX PROGRAMMER'S MANUAL.ps 12.vs 14p.sp 2.ft I.ceSixth Edition.sp 3.ce 3K. Thompson.sp .5D. M. Ritchie.sp 2.ceMay, 1975.sp 2.5i.ps 10.vs 12p.ft R.bp.sp 3i.sp 3i.ll 4.7i.in 1.5i.ft RThis manual was setby a Graphic Systems phototypesetter drivenby the \fItroff\fR formatting program operatingunder the \s8UNIX\s10 system.The text of the manual wasprepared using the \fIed\fR text editor..br.ft R.ll 6i.in 0.bp 1.sp 3.ce 2PREFACEto the Sixth Edition.sp.de CF.ro.tl ''%''.ar...sp 2We are gratefulto L. L. Cherry,R. C. Haight,S. C. Johnson,B. W. Kernighan,M. E. Lesk,andE. N. Pinsonfor theircontributionsto the system software,and to L. E. McMahon for software and forhis contributions to this manual.We are particularly appreciative of theinvaluable technical, editorial, and administrativeefforts ofJ. 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 supportincreased immeasurablynot only whatever success the \s8UNIX\s10 system enjoys,but also our own enjoyment in its creation..bp.sp 2.ceINTRODUCTION TO THIS MANUAL.pg.pgThis manual gives descriptions of the publicly availablefeatures of \s8UNIX\s10.It provides neither a generaloverview \- see ``The \s8UNIX\s10 Time-sharing System''(Comm. ACM \fB17\fR 7, July 1974, pp. 365-375)for that \-nor details of the implementation of the system, whichremain to be disclosed..pgWithin the area it surveys, this manual attemptsto be as complete and timely as possible.A consciousdecision was made to describe each programin exactly the state it was in at the timeits manual sectionwas prepared.In particular, thedesire to describe something as it should be, not as it is,was resisted.Inevitably, this means thatmany sections will soon be out of date..pgThis manual is divided intoeight sections:.pg.nf	I.	Commands	II.	System calls	III.	Subroutines	IV.	Special files	V.	File formats and conventions	VI.	User-maintained programs	VII.	User-maintained subroutines	VIII.	Maintenance.pg.fiCommands are programs intended to be invoked directly bythe user, in contradistinction to subroutines, which areintended to be called by the user's programs.Commands generally reside in directory.ft I/bin.ft R(for \fIbin\fR\|ary programs).Some programs also reside in.ft I/\|usr/\|bin,.ft Rto save space in\fI/bin.\fRThese directories are searched automatically by the command interpreter..pgSystem calls are entries into the \s8UNIX\s10 supervisor.In assembly language, they are coded with the useof the opcode \fIsys\fR, a synonym for the\fItrap\fR instruction.In this edition,the C language interface routines to the systemcalls have been incorporated in section II..pgA small assortmentof subroutines is available;they are described in section III.The binary form of most of them is kept inthe system library\fI/\|lib/\|liba.a.\fRThe subroutines available from C and from Fortran are also included;they reside in\fI/\|lib/\|libc.a\fRand\fI/\|lib/\|libf.a\fRrespectively..pgThe special files section IV discusses the characteristics ofeach system ``file'' which actually refers to an I/O device.The names in thissection refer to the DEC device names for thehardware,instead of the names ofthe special files themselves..pgThe file formats and conventions section V documents the structure of particularkinds of files; for example, the form of the output of the loader andassembler is given.  Excluded are files used by only one command,for example the assembler's intermediate files..pgUser-maintained programs and subroutines (sections VI and VII) are not considered partof the \s8UNIX\s10 system, and the principal reason forlisting them is to indicate their existence withoutnecessarily giving a complete description.The authors of the individual programs should be consultedfor more information..pgSection VIII discusses commands which are not intendedfor use by the ordinary user,in some cases because they disclose informationin which he is presumably not interested,and in others because they performprivileged functions..pg.pgEach section consists of a number of independententries 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 arealphabetized.The page numbers of each entry start at 1.(The earlier hope for frequent, partialupdates of the manual is clearly in vain, butin any event it is not feasible tomaintain consecutive page numbering in a documentlike this.).pgAll entries are based on a common format,not all of whose subsections will always appear..pg.in .5iThe \fIname\fR section repeats the entry name and givesa very short description of its purpose..pgThe \fIsynopsis\fR summarizes the use of theprogram being described.A few conventions are used, particularly in theCommands section:.pg.in 1i\fBBoldface\fR words are considered literals, andare typed just as they appear..pgSquare brackets ( [ ] ) around an argumentindicate that the argument is optional.When an argument is given as ``name'', it alwaysrefers to a file name..pgEllipses ``.\|.\|.'' are used to show that the previous argument-prototypemay be repeated..pgA final convention is used by the commands themselves.An argument beginning with a minus sign ``_''is often taken to mean some sort of flag argumenteven if it appears in a position where a file namecould appear.  Therefore, it is unwise to have fileswhose names begin with ``_''..pg.in .5iThe \fIdescription\fR section discusses in detail the subject at hand..pgThe \fIfiles\fR section gives the names of files which arebuilt into the program..pgA.ft Isee also.ft Rsection gives pointers to related information..pgA \fIdiagnostics\fRsection discussesthe diagnostic indications which may be produced.Messages which are intended to be self-explanatoryare not listed..pgThe \fIbugs\fR section givesknown bugs and sometimes deficiencies.Occasionally also the suggested fix isdescribed..pg.in 0At 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 titleof the writeup to whichit refers is followed by the appropriate section number in parentheses.This fact is important because there is considerablename duplication among the sections,arising principally from commands whichexist only to exercise a particular system call..pg.pgThis manual was prepared using the \s8UNIX\s10 texteditor \fIed\fR and the formatting program \fItroff\fR.