diff options
Diffstat (limited to 'usr.bin/file/file.1')
| -rw-r--r-- | usr.bin/file/file.1 | 87 |
1 files changed, 52 insertions, 35 deletions
diff --git a/usr.bin/file/file.1 b/usr.bin/file/file.1 index 9ba9aab30709..999d9e14b3a1 100644 --- a/usr.bin/file/file.1 +++ b/usr.bin/file/file.1 @@ -1,5 +1,5 @@ .TH FILE 1 "Copyright but distributable" -.\# $Id$ +.\" $Id: file.1,v 1.1.1.4 1997/03/18 17:58:59 mpp Exp $ .SH NAME file \- determine file type .SH SYNOPSIS @@ -15,7 +15,10 @@ namefile ] magicfiles ] file ... .SH DESCRIPTION -.I File +This manual page documents version 3.22 of the +.B file +command. +.B File tests each argument in an attempt to classify it. There are three sets of tests, performed in this order: filesystem tests, magic number tests, and language tests. @@ -25,8 +28,11 @@ test that succeeds causes the file type to be printed. .PP The type printed will usually contain one of the words .B text -(the file contains only ASCII characters and is -probably safe to read on an ASCII terminal), +(the file contains only +.SM ASCII +characters and is probably safe to read on an +.SM ASCII +terminal), .B executable (the file contains the result of compiling a program in a form understandable to some \s-1UNIX\s0 kernel or another), @@ -45,7 +51,7 @@ Don't do as Berkeley did \- change ``shell commands text'' to ``shell script''. .PP The filesystem tests are based on examining the return from a -.IR stat (2) +.BR stat (2) system call. The program checks to see if the file is empty, or if it's some sort of special file. @@ -54,16 +60,16 @@ Any known file types appropriate to the system you are running on implement them) are intuited if they are defined in the system header file -.BR sys/stat.h . +.IR sys/stat.h . .PP The magic number tests are used to check for files with data in particular fixed formats. The canonical example of this is a binary executable (compiled program) -.B a.out +.I a.out file, whose format is defined in -.B a.out.h +.I a.out.h and possibly -.B exec.h +.I exec.h in the standard include directory. These files have a `magic number' stored in a particular place near the beginning of the file that tells the \s-1UNIX\s0 operating system @@ -77,21 +83,23 @@ The information in these files is read from the magic file If an argument appears to be an .SM ASCII file, -.I file +.B file attempts to guess its language. -The language tests look for particular strings (cf \fInames.h\fP) +The language tests look for particular strings (cf +.IR names.h ) that can appear anywhere in the first few blocks of a file. For example, the keyword .B .br -indicates that the file is most likely a troff input file, -just as the keyword +indicates that the file is most likely a +.BR troff (1) +input file, just as the keyword .B struct indicates a C program. These tests are less reliable than the previous two groups, so they are performed last. The language test routines also test for some miscellany (such as -.I tar +.BR tar (1) archives) and determine whether an unknown file should be labelled as `ascii text' or `data'. .SH OPTIONS @@ -124,7 +132,7 @@ to test the standard input, use ``-'' as a filename argument. .TP 8 .B \-L option causes symlinks to be followed, as the like-named option in -.IR ls (1). +.BR ls (1). (on systems that support symbolic links). .SH FILES .I /etc/magic @@ -134,10 +142,10 @@ The environment variable .B MAGIC can be used to set the default magic number files. .SH SEE ALSO -.IR magic (5) +.BR magic (5) \- description of magic file format. .br -.IR strings (1), " od" (1) +.BR strings (1), " od" (1) \- tools for examining non-textfiles. .SH STANDARDS CONFORMANCE This program is believed to exceed the System V Interface Definition @@ -170,7 +178,7 @@ in an existing magic file would have to be changed to .br .PP SunOS releases 3.2 and later from Sun Microsystems include a -.IR file (1) +.BR file (1) command derived from the System V one, but with some extensions. My version differs from Sun's only in minor ways. It includes the extension of the `&' operator, used as, @@ -189,15 +197,15 @@ The order of entries in the magic file is significant. Depending on what system you are using, the order that they are put together may be incorrect. If your old -.I file +.B file command uses a magic file, keep the old magic file around for comparison purposes (rename it to .IR /etc/magic.orig ). .SH HISTORY There has been a -.I file -command in every UNIX since at least Research Version 6 +.B file +command in every \s-1UNIX\s0 since at least Research Version 6 (man page dated January, 1975). The System V version introduced one significant major change: the external list of magic number types. @@ -226,7 +234,7 @@ put the ``old-style'' `&' operator back the way it was, because 1) Rob McMahon's change broke the previous style of usage, 2) the SunOS ``new-style'' `&' operator, which this version of -.I file +.B file supports, also handles `x&y op z', and 3) Rob's change wasn't documented in any case; .PP @@ -235,11 +243,11 @@ put in multiple levels of `>'; put in ``beshort'', ``leshort'', etc. keywords to look at numbers in the file in a specific byte order, rather than in the native byte order of the process running -.IR file . +.BR file . .RE .PP Changes by Ian Darwin and various authors including -Christos Zoulas (christos@ee.cornell.edu), 1990-1992. +Christos Zoulas (christos@deshaw.com), 1990-1992. .SH LEGAL NOTICE Copyright (c) Ian F. Darwin, Toronto, Canada, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993. @@ -283,33 +291,42 @@ The files and .I is_tar.c were written by John Gilmore from his public-domain -.I tar +.B tar program, and are not covered by the above restrictions. .SH BUGS There must be a better way to automate the construction of the Magic file from all the glop in Magdir. What is it? Better yet, the magic file should be compiled into binary (say, -.IR ndbm (3) -or, better yet, fixed-length ASCII strings -for use in heterogenous network environments) for faster startup. +.BR ndbm (3) +or, better yet, fixed-length +.SM ASCII +strings for use in heterogenous network environments) for faster startup. Then the program would run as fast as the Version 7 program of the same name, with the flexibility of the System V version. .PP -.I File +.B File uses several algorithms that favor speed over accuracy, -thus it can be misled about the contents of ASCII files. +thus it can be misled about the contents of +.SM ASCII +files. .PP -The support for ASCII files (primarily for programming languages) +The support for +.SM ASCII +files (primarily for programming languages) is simplistic, inefficient and requires recompilation to update. .PP There should be an ``else'' clause to follow a series of continuation lines. .PP The magic file and keywords should have regular expression support. -Their use of ASCII TAB as a field delimiter is ugly and makes +Their use of +.SM "ASCII TAB" +as a field delimiter is ugly and makes it hard to edit the files, but is entrenched. .PP It might be advisable to allow upper-case letters in keywords -for e.g., troff commands vs man page macros. +for e.g., +.BR troff (1) +commands vs man page macros. Regular expression support would make this easy. .PP The program doesn't grok \s-2FORTRAN\s0. @@ -342,6 +359,6 @@ This manual page, and particularly this section, is too long. .SH AVAILABILITY You can obtain the original author's latest version by anonymous FTP on -.B tesla.ee.cornell.edu +.B ftp.deshaw.com in the directory -.BR /pub/file-X.YY.tar.gz +.I /pub/file/file-X.YY.tar.gz |