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diff --git a/man-pages-posix-2013/man1p/tail.1p b/man-pages-posix-2013/man1p/tail.1p new file mode 100644 index 0000000..28f5976 --- /dev/null +++ b/man-pages-posix-2013/man1p/tail.1p @@ -0,0 +1,348 @@ +'\" et +.TH TAIL "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 +tail +\(em copy the last part of a file +.SH SYNOPSIS +.LP +.nf +tail \fB[\fR\(mif\fB] [\fR\(mic \fInumber\fR|\(min \fInumber\fB] [\fIfile\fB]\fR +.fi +.SH DESCRIPTION +The +.IR tail +utility shall copy its input file to the standard output beginning at a +designated place. +.P +Copying shall begin at the point in the file indicated by the +.BR \(mic +.IR number +or +.BR \(min +.IR number +options. The option-argument +.IR number +shall be counted in units of lines or bytes, according to the options +.BR \(min +and +.BR \(mic . +Both line and byte counts start from 1. +.P +Tails relative to the end of the file may be saved in an internal +buffer, and thus may be limited in length. Such a buffer, if any, +shall be no smaller than +{LINE_MAX}*10 +bytes. +.SH OPTIONS +The +.IR tail +utility shall conform to the Base Definitions volume of POSIX.1\(hy2008, +.IR "Section 12.2" ", " "Utility Syntax Guidelines", +except that +.BR '\(pl' +may be recognized as an option delimiter as well as +.BR '\(mi' . +.P +The following options shall be supported: +.IP "\fB\(mic\ \fInumber\fR" 10 +The application shall ensure that the +.IR number +option-argument is a decimal integer, optionally including a sign. +The sign shall affect the location in the file, measured in bytes, +to begin the copying: +.TS +center tab(@) box; +cB | cB +cf5 | l. +Sign@Copying Starts +_ ++@Relative to the beginning of the file. +\(mi@Relative to the end of the file. +\fInone\fP@Relative to the end of the file. +.TE +.RS 10 +.P +The application shall ensure that if the sign of the +.IR number +option-argument is +.BR '\(pl' , +the +.IR number +option-argument is a non-zero decimal integer. +.P +The origin for counting shall be 1; that is, +.BR \(mic ++1 represents the first byte of the file, +.BR \(mic +\(mi1 the last. +.RE +.IP "\fB\(mif\fP" 10 +If the input file is a regular file or if the +.IR file +operand specifies a FIFO, do not terminate after the last line of the +input file has been copied, but read and copy further bytes from the +input file when they become available. If no +.IR file +operand is specified and standard input is a pipe or FIFO, the +.BR \(mif +option shall be ignored. If the input file is not a FIFO, pipe, or +regular file, it is unspecified whether or not the +.BR \(mif +option shall be ignored. +.IP "\fB\(min\ \fInumber\fR" 10 +This option shall be equivalent to +.BR \(mic +.IR number , +except the starting location in the file shall be measured in lines +instead of bytes. The origin for counting shall be 1; that is, +.BR \(min ++1 represents the first line of the file, +.BR \(min +\(mi1 the last. +.P +If neither +.BR \(mic +nor +.BR \(min +is specified, +.BR \(min +10 shall be assumed. +.SH OPERANDS +The following operand shall be supported: +.IP "\fIfile\fR" 10 +A pathname of an input file. If no +.IR file +operand is specified, the standard input shall be used. +.SH STDIN +The standard input shall be used if no +.IR file +operand is specified, and shall be used if the +.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. +See the INPUT FILES section. +.SH "INPUT FILES" +If the +.BR \(mic +option is specified, the input file can contain arbitrary data; +otherwise, the input file shall be a text file. +.SH "ENVIRONMENT VARIABLES" +The following environment variables shall affect the execution of +.IR tail : +.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. +.IP "\fINLSPATH\fP" 10 +Determine the location of message catalogs for the processing of +.IR LC_MESSAGES . +.SH "ASYNCHRONOUS EVENTS" +Default. +.SH STDOUT +The designated portion of the input file shall be written to standard +output. +.SH STDERR +The standard error shall be used only for diagnostic messages. +.SH "OUTPUT FILES" +None. +.SH "EXTENDED DESCRIPTION" +None. +.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 +.BR \(mic +option should be used with caution when the input is a text file +containing multi-byte characters; it may produce output that does not +start on a character boundary. +.P +Although the input file to +.IR tail +can be any type, the results might not be what would be expected on +some character special device files or on file types not described by +the System Interfaces volume of POSIX.1\(hy2008. Since this volume of POSIX.1\(hy2008 does not specify the block size used when doing +input, +.IR tail +need not read all of the data from devices that only perform block +transfers. +.SH EXAMPLES +The +.BR \(mif +option can be used to monitor the growth of a file that is being +written by some other process. For example, the command: +.sp +.RS 4 +.nf +\fB +tail \(mif fred +.fi \fR +.P +.RE +.P +prints the last ten lines of the file +.BR fred , +followed by any lines that are appended to +.BR fred +between the time +.IR tail +is initiated and killed. As another example, the command: +.sp +.RS 4 +.nf +\fB +tail \(mif \(mic 15 fred +.fi \fR +.P +.RE +.P +prints the last 15 bytes of the file +.BR fred , +followed by any bytes that are appended to +.BR fred +between the time +.IR tail +is initiated and killed. +.SH RATIONALE +This version of +.IR tail +was created to allow conformance to the Utility Syntax Guidelines. The +historical +.BR \(mib +option was omitted because of the general non-portability of block-sized +units of text. The +.BR \(mic +option historically meant ``characters'', but this volume of POSIX.1\(hy2008 indicates +that it means ``bytes''. This was selected to allow reasonable +implementations when multi-byte characters are possible; it was not +named +.BR \(mib +to avoid confusion with the historical +.BR \(mib . +.P +The origin of counting both lines and bytes is 1, matching all +widespread historical implementations. Hence +.IR tail +.BR \(min ++0 is not conforming usage because it attempts to output line zero; but +note that +.IR tail +.BR \(min +0 does conform, and outputs nothing. +.P +Earlier versions of this standard allowed the following forms in the +SYNOPSIS: +.sp +.RS 4 +.nf +\fB +tail \(mi\fB[\fRnumber\fB][\fRb|c|l\fB][\fRf\fB] [\fIfile\fB]\fR +tail \(pl\fB[\fRnumber\fB][\fRb|c|l\fB][\fRf\fB] [\fIfile\fB]\fR +.fi \fR +.P +.RE +.P +These forms are no longer specified by POSIX.1\(hy2008, but may be +present in some implementations. +.P +The restriction on the internal buffer is a compromise between the +historical System V implementation of 4\|096 bytes and the BSD 32\|768 +bytes. +.P +The +.BR \(mif +option has been implemented as a loop that sleeps for 1 second and +copies any bytes that are available. This is sufficient, but if more +efficient methods of determining when new data are available are +developed, implementations are encouraged to use them. +.P +Historical documentation indicates that +.IR tail +ignores the +.BR \(mif +option if the input file is a pipe (pipe and FIFO on systems that +support FIFOs). On BSD-based systems, this has been true; on System +V-based systems, this was true when input was taken from standard +input, but it did not ignore the +.BR \(mif +flag if a FIFO was named as the +.IR file +operand. Since the +.BR \(mif +option is not useful on pipes and all historical implementations ignore +.BR \(mif +if no +.IR file +operand is specified and standard input is a pipe, this volume of POSIX.1\(hy2008 requires this +behavior. However, since the +.BR \(mif +option is useful on a FIFO, this volume of POSIX.1\(hy2008 also requires that +if a FIFO is named, the +.BR \(mif +option shall not be ignored. Earlier versions of this standard did +not state any requirement for the case where no +.IR file +operand is specified and standard input is a FIFO. The standard has +been updated to reflect current practice which is to treat this case +the same as a pipe on standard input. +Although historical behavior does not ignore the +.BR \(mif +option for other file types, this is unspecified so that +implementations are allowed to ignore the +.BR \(mif +option if it is known that the file cannot be extended. +.SH "FUTURE DIRECTIONS" +None. +.SH "SEE ALSO" +.IR "\fIhead\fR\^" +.P +The Base Definitions volume of POSIX.1\(hy2008, +.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 . |