.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved .TH "CMP" 1P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" .\" cmp .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 cmp \- compare two files .SH SYNOPSIS .LP \fBcmp\fP \fB[\fP \fB-l | -s\fP \fB]\fP \fIfile1 file2\fP .SH DESCRIPTION .LP The \fIcmp\fP utility shall compare two files. The \fIcmp\fP utility shall write no output if the files are the same. Under default options, if they differ, it shall write to standard output the byte and line number at which the first difference occurred. Bytes and lines shall be numbered beginning with 1. .SH OPTIONS .LP The \fIcmp\fP utility shall conform to the Base Definitions volume of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines. .LP The following options shall be supported: .TP 7 \fB-l\fP (Lowercase ell.) Write the byte number (decimal) and the differing bytes (octal) for each difference. .TP 7 \fB-s\fP Write nothing for differing files; return exit status only. .sp .SH OPERANDS .LP The following operands shall be supported: .TP 7 \fIfile1\fP A pathname of the first file to be compared. If \fIfile1\fP is \fB'-'\fP, the standard input shall be used. .TP 7 \fIfile2\fP A pathname of the second file to be compared. If \fIfile2\fP is \fB'-'\fP, the standard input shall be used. .sp .LP If both \fIfile1\fP and \fIfile2\fP refer to standard input or refer to the same FIFO special, block special, or character special file, the results are undefined. .SH STDIN .LP The standard input shall be used only if the \fIfile1\fP or \fIfile2\fP operand refers to standard input. See the INPUT FILES section. .SH INPUT FILES .LP The input files can be any file type. .SH ENVIRONMENT VARIABLES .LP The following environment variables shall affect the execution of \fIcmp\fP: .TP 7 \fILANG\fP Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) .TP 7 \fILC_ALL\fP If set to a non-empty string value, override the values of all the other internationalization variables. .TP 7 \fILC_CTYPE\fP 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). .TP 7 \fILC_MESSAGES\fP 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. .TP 7 \fINLSPATH\fP Determine the location of message catalogs for the processing of \fILC_MESSAGES \&.\fP .sp .SH ASYNCHRONOUS EVENTS .LP Default. .SH STDOUT .LP In the POSIX locale, results of the comparison shall be written to standard output. When no options are used, the format shall be: .sp .RS .nf \fB"%s %s differ: char %d, line %d\\n",\fP \fIfile1\fP\fB,\fP \fIfile2\fP\fB, <\fP\fIbyte number\fP\fB>, <\fP\fIline number\fP\fB> \fP .fi .RE .LP When the \fB-l\fP option is used, the format shall be: .sp .RS .nf \fB"%d %o %o\\n", <\fP\fIbyte number\fP\fB>, <\fP\fIdiffering byte\fP\fB>, <\fP\fIdiffering byte\fP\fB> \fP .fi .RE .LP for each byte that differs. The first <\fIdiffering\ byte\fP> number is from \fIfile1\fP while the second is from \fIfile2\fP. In both cases, <\fIbyte\ number\fP> shall be relative to the beginning of the file, beginning with 1. .LP No output shall be written to standard output when the \fB-s\fP option is used. .SH STDERR .LP The standard error shall be used only for diagnostic messages. If \fIfile1\fP and \fIfile2\fP are identical for the entire length of the shorter file, in the POSIX locale the following diagnostic message shall be written, unless the \fB-s\fP option is specified: .sp .RS .nf \fB"cmp: EOF on %s%s\\n", <\fP\fIname of shorter file\fP\fB>, <\fP\fIadditional info\fP\fB> \fP .fi .RE .LP The <\fIadditional\ info\fP> field shall either be null or a string that starts with a and contains no s. Some implementations report on the number of lines in this case. .SH OUTPUT FILES .LP None. .SH EXTENDED DESCRIPTION .LP None. .SH EXIT STATUS .LP The following exit values shall be returned: .TP 7 \ 0 The files are identical. .TP 7 \ 1 The files are different; this includes the case where one file is identical to the first part of the other. .TP 7 >1 An error occurred. .sp .SH CONSEQUENCES OF ERRORS .LP Default. .LP \fIThe following sections are informative.\fP .SH APPLICATION USAGE .LP Although input files to \fIcmp\fP can be any type, the results might not be what would be expected on character special device files or on file types not described by the System Interfaces volume of IEEE\ Std\ 1003.1-2001. Since this volume of IEEE\ Std\ 1003.1-2001 does not specify the block size used when doing input, comparisons of character special files need not compare all of the data in those files. .LP For files which are not text files, line numbers simply reflect the presence of a , without any implication that the file is organized into lines. .SH EXAMPLES .LP None. .SH RATIONALE .LP The global language in \fIUtility Description Defaults\fP indicates that using two mutually-exclusive options together produces unspecified results. Some System V implementations consider the option usage: .sp .RS .nf \fBcmp -l -s ... \fP .fi .RE .LP to be an error. They also treat: .sp .RS .nf \fBcmp -s -l ... \fP .fi .RE .LP as if no options were specified. Both of these behaviors are considered bugs, but are allowed. .LP The word \fBchar\fP in the standard output format comes from historical usage, even though it is actually a byte number. When \fIcmp\fP is supported in other locales, implementations are encouraged to use the word \fIbyte\fP or its equivalent in another language. Users should not interpret this difference to indicate that the functionality of the utility changed between locales. .LP Some implementations report on the number of lines in the identical-but-shorter file case. This is allowed by the inclusion of the <\fIadditional\ info\fP> fields in the output format. The restriction on having a leading and no s is to make parsing for the filename easier. It is recognized that some filenames containing white-space characters make parsing difficult anyway, but the restriction does aid programs used on systems where the names are predominantly well behaved. .SH FUTURE DIRECTIONS .LP None. .SH SEE ALSO .LP \fIcomm\fP, \fIdiff\fP .SH COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .