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diff --git a/man-pages-posix-2013/man1p/file.1p b/man-pages-posix-2013/man1p/file.1p new file mode 100644 index 0000000..3353707 --- /dev/null +++ b/man-pages-posix-2013/man1p/file.1p @@ -0,0 +1,829 @@ +'\" et +.TH FILE "1P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual" +.SH PROLOG +This manual page is part of the POSIX Programmer's Manual. +The Linux implementation of this interface may differ (consult +the corresponding Linux manual page for details of Linux behavior), +or the interface may not be implemented on Linux. + +.SH NAME +file +\(em determine file type +.SH SYNOPSIS +.LP +.nf +file \fB[\fR\(midh\fB] [\fR\(miM \fIfile\fB] [\fR\(mim \fIfile\fB] \fIfile\fR... +.P +file \(mii \fB[\fR\(mih\fB] \fIfile\fR... +.fi +.SH DESCRIPTION +The +.IR file +utility shall perform a series of tests in sequence on each specified +.IR file +in an attempt to classify it: +.IP " 1." 4 +If +.IR file +does not exist, cannot be read, or its file status could not be +determined, the output shall indicate that the file was processed, but +that its type could not be determined. +.IP " 2." 4 +If the file is not a regular file, its file type shall be identified. +The file types directory, FIFO, socket, block special, and character +special shall be identified as such. Other implementation-defined file +types may also be identified. If +.IR file +is a symbolic link, by default the link shall be resolved and +.IR file +shall test the type of file referenced by the symbolic link. (See the +.BR \(mih +and +.BR \(mii +options below.) +.IP " 3." 4 +If the length of +.IR file +is zero, it shall be identified as an empty file. +.IP " 4." 4 +The +.IR file +utility shall examine an initial segment of +.IR file +and shall make a guess at identifying its contents based on +position-sensitive tests. (The answer is not guaranteed to be correct; +see the +.BR \(mid , +.BR \(miM , +and +.BR \(mim +options below.) +.IP " 5." 4 +The +.IR file +utility shall examine +.IR file +and make a guess at identifying its contents based on context-sensitive +default system tests. (The answer is not guaranteed to be correct.) +.IP " 6." 4 +The file shall be identified as a data file. +.P +If +.IR file +does not exist, cannot be read, or its file status could not be +determined, the output shall indicate that the file was processed, but +that its type could not be determined. +.P +If +.IR file +is a symbolic link, by default the link shall be resolved and +.IR file +shall test the type of file referenced by the symbolic link. +.SH OPTIONS +The +.IR file +utility shall conform to the Base Definitions volume of POSIX.1\(hy2008, +.IR "Section 12.2" ", " "Utility Syntax Guidelines", +except that the order of the +.BR \(mim , +.BR \(mid , +and +.BR \(miM +options shall be significant. +.P +The following options shall be supported by the implementation: +.IP "\fB\(mid\fP" 10 +Apply any position-sensitive default system tests and +context-sensitive default system tests to the file. This is the +default if no +.BR \(miM +or +.BR \(mim +option is specified. +.IP "\fB\(mih\fP" 10 +When a symbolic link is encountered, identify the file as a symbolic +link. If +.BR \(mih +is not specified and +.IR file +is a symbolic link that refers to a nonexistent file, +.IR file +shall identify the file as a symbolic link, as if +.BR \(mih +had been specified. +.IP "\fB\(mii\fP" 10 +If a file is a regular file, do not attempt to classify the type of the +file further, but identify the file as specified in the STDOUT section. +.IP "\fB\(miM\ \fIfile\fR" 10 +Specify the name of a file containing position-sensitive tests that +shall be applied to a file in order to classify it (see the EXTENDED +DESCRIPTION). No position-sensitive default system tests nor +context-sensitive default system tests shall be applied unless the +.BR \(mid +option is also specified. +.IP "\fB\(mim\ \fIfile\fR" 10 +Specify the name of a file containing position-sensitive tests that +shall be applied to a file in order to classify it (see the EXTENDED +DESCRIPTION). +.P +If the +.BR \(mim +option is specified without specifying the +.BR \(mid +option or the +.BR \(miM +option, position-sensitive default system tests shall be applied after +the position-sensitive tests specified by the +.BR \(mim +option. If the +.BR \(miM +option is specified with the +.BR \(mid +option, the +.BR \(mim +option, or both, or the +.BR \(mim +option is specified with the +.BR \(mid +option, the concatenation of the position-sensitive tests specified by +these options shall be applied in the order specified by the appearance +of these options. If a +.BR \(miM +or +.BR \(mim +.IR file +option-argument is +.BR \(mi , +the results are unspecified. +.SH OPERANDS +The following operand shall be supported: +.IP "\fIfile\fR" 10 +A pathname of a file to be tested. +.SH STDIN +The standard input shall be used if a +.IR file +operand is +.BR '\(mi' +and the implementation treats the +.BR '\(mi' +as meaning standard input. +Otherwise, the standard input shall not be used. +.SH "INPUT FILES" +The +.IR file +can be any file type. +.SH "ENVIRONMENT VARIABLES" +The following environment variables shall affect the execution of +.IR file : +.IP "\fILANG\fP" 10 +Provide a default value for the internationalization variables that are +unset or null. (See the Base Definitions volume of POSIX.1\(hy2008, +.IR "Section 8.2" ", " "Internationalization Variables" +for the precedence of internationalization variables used to determine +the values of locale categories.) +.IP "\fILC_ALL\fP" 10 +If set to a non-empty string value, override the values of all the +other internationalization variables. +.IP "\fILC_CTYPE\fP" 10 +Determine the locale for the interpretation of sequences of bytes of +text data as characters (for example, single-byte as opposed to +multi-byte characters in arguments and input files). +.IP "\fILC_MESSAGES\fP" 10 +.br +Determine the locale that should be used to affect the format and +contents of diagnostic messages written to standard error and +informative messages written to standard output. +.IP "\fINLSPATH\fP" 10 +Determine the location of message catalogs for the processing of +.IR LC_MESSAGES . +.SH "ASYNCHRONOUS EVENTS" +Default. +.SH STDOUT +In the POSIX locale, the following format shall be used to identify +each operand, +.IR file +specified: +.sp +.RS 4 +.nf +\fB +"%s: %s\en", <\fIfile\fR>, <\fItype\fR> +.fi \fR +.P +.RE +.P +The values for <\fItype\fP> are unspecified, except that in the POSIX +locale, if +.IR file +is identified as one of the types listed in the following table, +<\fItype\fP> shall contain (but is not limited to) the corresponding +string, unless the file is identified by a position-sensitive test +specified by a +.BR \(miM +or +.BR \(mim +option. Each +<space> +shown in the strings shall be exactly one +<space>. +.br +.sp +.ce 1 +\fBTable 4-9: File Utility Output Strings\fR +.TS +center tab(@) box; +cB | cB | cB +l | l | l. +If \fIfile\fP is:@<\fItype\fP> shall contain the string:@Notes +_ +Nonexistent@cannot open +.P +Block special@block special@1 +Character special@character special@1 +Directory@directory@1 +FIFO@fifo@1 +Socket@socket@1 +Symbolic link@symbolic link to@1 +Regular file@regular file@1,2 +Empty regular file@empty@3 +Regular file that cannot be read@cannot open@3 +.P +Executable binary@executable@3,4,6 +\fIar\fR archive library (see \fIar\fP)@archive@3,4,6 +Extended \fIcpio\fP format (see \fIpax\fP)@cpio archive@3,4,6 +Extended \fItar\fP format (see \fBustar\fP in \fIpax\fP)@tar archive@3,4,6 +.P +Shell script@commands text@3,5,6 +C-language source@c program text@3,5,6 +FORTRAN source@fortran program text@3,5,6 +.P +Regular file whose type cannot be determined@data@3 +.TE +.TP 10 +.BR Notes: +.RS 10 +.IP " 1." 4 +This is a file type test. +.IP " 2." 4 +This test is applied only if the +.BR \(mii +option is specified. +.IP " 3." 4 +This test is applied only if the +.BR \(mii +option is not specified. +.IP " 4." 4 +This is a position-sensitive default system test. +.IP " 5." 4 +This is a context-sensitive default system test. +.IP " 6." 4 +Position-sensitive default system tests and context-sensitive +default system tests are not applied if the +.BR \(miM +option is specified unless the +.BR \(mid +option is also specified. +.RE +.P +.P +In the POSIX locale, if +.IR file +is identified as a symbolic link (see the +.BR \(mih +option), the following alternative output format shall be used: +.sp +.RS 4 +.nf +\fB +"%s: %s %s\en", <\fIfile\fR>, <\fItype\fR>, <\fIcontents of link\fR>" +.fi \fR +.P +.RE +.P +If the file named by the +.IR file +operand does not exist, cannot be read, or the type of the file named +by the +.IR file +operand cannot be determined, this shall not be considered an error +that affects the exit status. +.SH STDERR +The standard error shall be used only for diagnostic messages. +.SH "OUTPUT FILES" +None. +.SH "EXTENDED DESCRIPTION" +A file specified as an option-argument to the +.BR \(mim +or +.BR \(miM +options shall contain one position-sensitive test per line, which shall +be applied to the file. If the test succeeds, the message field of the +line shall be printed and no further tests shall be applied, with the +exception that tests on immediately following lines beginning with a +single +.BR '>' +character shall be applied. +.P +Each line shall be composed of the following four +<tab>-separated +fields. (Implementations may allow any combination of one or more +white-space characters other than +<newline> +to act as field separators.) +.IP "\fIoffset\fP" 10 +An unsigned number (optionally preceded by a single +.BR '>' +character) specifying the +.IR offset , +in bytes, of the value in the file that is to be compared against the +.IR value +field of the line. If the file is shorter than the specified offset, +the test shall fail. +.RS 10 +.P +If the +.IR offset +begins with the character +.BR '>' , +the test contained in the line shall not be applied to the file unless +the test on the last line for which the +.IR offset +did not begin with a +.BR '>' +was successful. By default, the +.IR offset +shall be interpreted as an unsigned decimal number. With a leading 0x +or 0X, the +.IR offset +shall be interpreted as a hexadecimal number; otherwise, with a leading +0, the +.IR offset +shall be interpreted as an octal number. +.RE +.IP "\fItype\fP" 10 +The type of the value in the file to be tested. The type shall consist +of the type specification characters +.BR d , +.BR s , +and +.BR u , +specifying signed decimal, string, and unsigned decimal, respectively. +.RS 10 +.P +The +.IR type +string shall be interpreted as the bytes from the file starting at the +specified +.IR offset +and including the same number of bytes specified by the +.IR value +field. If insufficient bytes remain in the file past the +.IR offset +to match the +.IR value +field, the test shall fail. +.P +The type specification characters +.BR d +and +.BR u +can be followed by an optional unsigned decimal integer that specifies +the number of bytes represented by the type. The type specification +characters +.BR d +and +.BR u +can be followed by an optional +.BR C , +.BR S , +.BR I , +or +.BR L , +indicating that the value is of type +.BR char , +.BR short , +.BR int , +or +.BR long , +respectively. +.P +The default number of bytes represented by the type specifiers +.BR d , +.BR f , +and +.BR u +shall correspond to their respective C-language types as follows. If +the system claims conformance to the C-Language Development Utilities +option, those specifiers shall correspond to the default sizes used in +the +.IR c99 +utility. Otherwise, the default sizes shall be implementation-defined. +.P +For the type specifier characters +.BR d +and +.BR u , +the default number of bytes shall correspond to the size of a basic +integer type of the implementation. For these specifier +characters, the implementation shall support values of the optional +number of bytes to be converted corresponding to the number of bytes in +the C-language types +.BR char , +.BR short , +.BR int , +or +.BR long . +These numbers can also be specified by an application as the characters +.BR C , +.BR S , +.BR I , +and +.BR L , +respectively. The byte order used when interpreting numeric values is +implementation-defined, but shall correspond to the order in which a +constant of the corresponding type is stored in memory on the system. +.P +All type specifiers, except for +.BR s , +can be followed by a mask specifier of the form &\fInumber\fP. The mask +value shall be AND'ed with the value of the input file before the +comparison with the +.IR value +field of the line is made. By default, the mask shall be interpreted as +an unsigned decimal number. With a leading 0x or 0X, the mask shall be +interpreted as an unsigned hexadecimal number; otherwise, with a +leading 0, the mask shall be interpreted as an unsigned octal number. +.P +The strings +.BR byte , +.BR short , +.BR long , +and +.BR string +shall also be supported as type fields, being interpreted as +.BR dC , +.BR dS , +.BR dL , +and +.BR s , +respectively. +.RE +.IP "\fIvalue\fP" 10 +The +.IR value +to be compared with the value from the file. +.RS 10 +.P +If the specifier from the type field is +.BR s +or +.BR string , +then interpret the value as a string. Otherwise, interpret it as a +number. If the value is a string, then the test shall succeed only when +a string value exactly matches the bytes from the file. +.P +If the +.IR value +is a string, it can contain the following sequences: +.IP "\e\fIcharacter\fR" 12 +The +<backslash>-escape +sequences as specified in the Base Definitions volume of POSIX.1\(hy2008, +.IR "Table 5-1" ", " "Escape Sequences and Associated Actions" +(\c +.BR '\e\e' , +.BR '\ea' , +.BR '\eb' , +.BR '\ef' , +.BR '\en' , +.BR '\er' , +.BR '\et' , +.BR '\ev' ). +In addition, the escape sequence +.BR '\e\ ' +(the +<backslash> +character followed by a +<space> +character) shall be recognized to represent a +<space> +character. The results of using any other character, other than an +octal digit, following the +<backslash> +are unspecified. +.IP "\e\fIoctal\fR" 12 +Octal sequences that can be used to represent characters with specific +coded values. An octal sequence shall consist of a +<backslash> +followed by the longest sequence of one, two, or three octal-digit +characters (01234567). +.P +By default, any value that is not a string shall be interpreted as a +signed decimal number. Any such value, with a leading 0x or 0X, shall +be interpreted as an unsigned hexadecimal number; otherwise, with a +leading zero, the value shall be interpreted as an unsigned octal +number. +.P +If the value is not a string, it can be preceded by a character +indicating the comparison to be performed. Permissible characters and +the comparisons they specify are as follows: +.IP "\fR=\fP" 6 +The test shall succeed if the value from the file equals the +.IR value +field. +.IP "\fR<\fP" 6 +The test shall succeed if the value from the file is less than the +.IR value +field. +.IP "\fR>\fP" 6 +The test shall succeed if the value from the file is greater than the +.IR value +field. +.IP "\fR&\fP" 6 +The test shall succeed if all of the set bits in the +.IR value +field are set in the value from the file. +.IP "\fR^\fP" 6 +The test shall succeed if at least one of the set bits in the +.IR value +field is not set in the value from the file. +.IP "\fRx\fP" 6 +The test shall succeed if the file is large enough to contain a value +of the type specified starting at the offset specified. +.RE +.IP "\fImessage\fP" 10 +The +.IR message +to be printed if the test succeeds. The +.IR message +shall be interpreted using the notation for the +.IR printf +formatting specification; see +.IR printf . +If the +.IR value +field was a string, then the value from the file shall be the argument +for the +.IR printf +formatting specification; otherwise, the value from the file shall be +the argument. +.br +.SH "EXIT STATUS" +The following exit values shall be returned: +.IP "\00" 6 +Successful completion. +.IP >0 6 +An error occurred. +.SH "CONSEQUENCES OF ERRORS" +Default. +.LP +.IR "The following sections are informative." +.SH "APPLICATION USAGE" +The +.IR file +utility can only be required to guess at many of the file types because +only exhaustive testing can determine some types with certainty. For +example, binary data on some implementations might match the initial +segment of an executable or a +.IR tar +archive. +.P +Note that the table indicates that the output contains the stated +string. Systems may add text before or after the string. For +executables, as an example, the machine architecture and various facts +about how the file was link-edited may be included. Note also that on +systems that recognize shell script files starting with +.BR \(dq#!\(dq +as executable files, these may be identified as executable binary files +rather than as shell scripts. +.SH EXAMPLES +Determine whether an argument is a binary executable file: +.sp +.RS 4 +.nf +\fB +file \(mi\|\(mi "$1" | grep \(miq ':.*executable' && + printf "%s is executable.\en$1" +.fi \fR +.P +.RE +.SH RATIONALE +The +.BR \(mif +option was omitted because the same effect can (and should) be obtained +using the +.IR xargs +utility. +.P +Historical versions of the +.IR file +utility attempt to identify the following types of files: symbolic +link, directory, character special, block special, socket, +.IR tar +archive, +.IR cpio +archive, SCCS archive, archive library, empty, +.IR compress +output, +.IR pack +output, binary data, C source, FORTRAN source, assembler source, +.IR nroff /\c +.IR troff /\c +.IR eqn /\c +.IR tbl +source +.IR troff +output, shell script, C shell script, English text, ASCII text, various +executables, APL workspace, compiled terminfo entries, and CURSES +screen images. Only those types that are reasonably well specified in +POSIX or are directly related to POSIX utilities are listed in the +table. +.P +Historical systems have used a ``magic file'' named +.BR /etc/magic +to help identify file types. Because it is generally useful for users +and scripts to be able to identify special file types, the +.BR \(mim +flag and a portable format for user-created magic files has been +specified. No requirement is made that an implementation of +.IR file +use this method of identifying files, only that users be permitted to +add their own classifying tests. +.P +In addition, three options have been added to historical practice. The +.BR \(mid +flag has been added to permit users to cause their tests to follow any +default system tests. The +.BR \(mii +flag has been added to permit users to test portably for regular files +in shell scripts. The +.BR \(miM +flag has been added to permit users to ignore any default system +tests. +.P +The POSIX.1\(hy2008 description of default system tests and the interaction +between the +.BR \(mid , +.BR \(miM , +and +.BR \(mim +options did not clearly indicate that there were two types of ``default +system tests''. The ``position-sensitive tests'' determine file types +by looking for certain string or binary values at specific offsets in +the file being examined. These position-sensitive tests were +implemented in historical systems using the magic file described above. +Some of these tests are now built into the +.IR file +utility itself on some implementations so the output can provide more +detail than can be provided by magic files. For example, a magic file +can easily identify a +.BR core +file on most implementations, but cannot name the program file that +dropped the core. A magic file could produce output such as: +.sp +.RS 4 +.nf +\fB +/home/dwc/core: ELF 32-bit MSB core file SPARC Version 1 +.fi \fR +.P +.RE +.P +but by building the test into the +.IR file +utility, you could get output such as: +.sp +.RS 4 +.nf +\fB +/home/dwc/core: ELF 32-bit MSB core file SPARC Version 1, from 'testprog' +.fi \fR +.P +.RE +.P +These extended built-in tests are still to be treated as +position-sensitive default system tests even if they are not listed in +.BR /etc/magic +or any other magic file. +.P +The context-sensitive default system tests were always built into the +.IR file +utility. These tests looked for language constructs in text files +trying to identify shell scripts, C, FORTRAN, and other computer +language source files, and even plain text files. With the addition of +the +.BR \(mim +and +.BR \(miM +options the distinction between position-sensitive and +context-sensitive default system tests became important because the +order of testing is important. The context-sensitive system default +tests should never be applied before any position-sensitive tests even +if the +.BR \(mid +option is specified before a +.BR \(mim +option or +.BR \(miM +option due to the high probability that the context-sensitive system +default tests will incorrectly identify arbitrary text files as text +files before position-sensitive tests specified by the +.BR \(mim +or +.BR \(miM +option would be applied to give a more accurate identification. +.P +Leaving the meaning of +.BR "\(miM \(mi" +and +.BR "\(mim \(mi" +unspecified allows an existing prototype of these options to continue +to work in a backwards-compatible manner. (In that implementation, +.BR "\(miM \(mi" +was roughly equivalent to +.BR \(mid +in POSIX.1\(hy2008.) +.P +The historical +.BR \(mic +option was omitted as not particularly useful to users or portable +shell scripts. In addition, a reasonable implementation of the +.IR file +utility would report any errors found each time the magic file is +read. +.P +The historical format of the magic file was the same as that specified +by the Rationale in the ISO\ POSIX\(hy2:\|1993 standard for the +.IR offset , +.IR value , +and +.IR message +fields; however, it used less precise type fields than the format +specified by the current normative text. The new type field values are +a superset of the historical ones. +.P +The following is an example magic file: +.sp +.RS 4 +.nf +\fB +0 short 070707 cpio archive +0 short 0143561 Byte-swapped cpio archive +0 string 070707 ASCII cpio archive +0 long 0177555 Very old archive +0 short 0177545 Old archive +0 short 017437 Old packed data +0 string \e037\e036 Packed data +0 string \e377\e037 Compacted data +0 string \e037\e235 Compressed data +>2 byte&0x80 >0 Block compressed +>2 byte&0x1f x %d bits +0 string \e032\e001 Compiled Terminfo Entry +0 short 0433 Curses screen image +0 short 0434 Curses screen image +0 string <ar> System V Release 1 archive +0 string !<arch>\en__.SYMDEF Archive random library +0 string !<arch> Archive +0 string ARF_BEGARF PHIGS clear text archive +0 long 0x137A2950 Scalable OpenFont binary +0 long 0x137A2951 Encrypted scalable OpenFont binary +.fi \fR +.P +.RE +.P +The use of a basic integer data type is intended to allow the +implementation to choose a word size commonly used by applications +on that architecture. +.P +Earlier versions of this standard allowed for implementations with +bytes other than eight bits, but this has been modified in this +version. +.SH "FUTURE DIRECTIONS" +None. +.SH "SEE ALSO" +.IR "\fIar\fR\^", +.IR "\fIls\fR\^", +.IR "\fIpax\fR\^", +.IR "\fIprintf\fR\^" +.P +The Base Definitions volume of POSIX.1\(hy2008, +.IR "Table 5-1" ", " "Escape Sequences and Associated Actions", +.IR "Chapter 8" ", " "Environment Variables", +.IR "Section 12.2" ", " "Utility Syntax Guidelines" +.SH COPYRIGHT +Portions of this text are reprinted and reproduced in electronic form +from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology +-- Portable Operating System Interface (POSIX), The Open Group Base +Specifications Issue 7, Copyright (C) 2013 by the Institute of +Electrical and Electronics Engineers, Inc and The Open Group. +(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the +event of any discrepancy between this version and the original IEEE and +The Open Group Standard, the original IEEE and The Open Group Standard +is the referee document. The original Standard can be obtained online at +http://www.unix.org/online.html . + +Any typographical or formatting errors that appear +in this page are most likely +to have been introduced during the conversion of the source files to +man page format. To report such errors, see +https://www.kernel.org/doc/man-pages/reporting_bugs.html . |