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diff --git a/man1p/tail.1p b/man1p/tail.1p new file mode 100644 index 000000000..515d18ea9 --- /dev/null +++ b/man1p/tail.1p @@ -0,0 +1,249 @@ +.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved +.TH "TAIL" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" +.\" tail +.SH NAME +tail \- copy the last part of a file +.SH SYNOPSIS +.LP +\fBtail\fP \fB[\fP\fB-f\fP\fB][\fP \fB-c\fP \fInumber\fP\fB| -n\fP +\fInumber\fP\fB][\fP\fIfile\fP\fB]\fP +.SH DESCRIPTION +.LP +The \fItail\fP utility shall copy its input file to the standard output +beginning at a designated place. +.LP +Copying shall begin at the point in the file indicated by the \fB-c\fP +\fInumber\fP or \fB-n\fP \fInumber\fP options. The +option-argument \fInumber\fP shall be counted in units of lines or +bytes, according to the options \fB-n\fP and \fB-c\fP. Both +line and byte counts start from 1. +.LP +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 +.LP +The \fItail\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-c\ \fP \fInumber\fP +The application shall ensure that the \fInumber\fP option-argument +is a decimal integer whose sign affects the location in the +file, measured in bytes, to begin the copying: +.TS C +center; l l. +\fBSign\fP \fBCopying Starts\fP ++ Relative to the beginning of the file. +- Relative to the end of the file. +\fInone\fP Relative to the end of the file. +.TE +.LP +The origin for counting shall be 1; that is, \fB-c\fP +1 represents +the first byte of the file, \fB-c\fP -1 the last. +.TP 7 +\fB-f\fP +If the input file is a regular file or if the \fIfile\fP 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 \fIfile\fP +operand is specified and standard input is a pipe, the \fB-f\fP option +shall be ignored. If the input file is not a FIFO, pipe, or +regular file, it is unspecified whether or not the \fB-f\fP option +shall be ignored. +.TP 7 +\fB-n\ \fP \fInumber\fP +This option shall be equivalent to \fB-c\fP \fInumber\fP, except the +starting location in the file shall be measured in lines +instead of bytes. The origin for counting shall be 1; that is, \fB-n\fP ++1 represents the first line of the file, \fB-n\fP -1 the +last. +.sp +.LP +If neither \fB-c\fP nor \fB-n\fP is specified, \fB-n\fP 10 shall be +assumed. +.SH OPERANDS +.LP +The following operand shall be supported: +.TP 7 +\fIfile\fP +A pathname of an input file. If no \fIfile\fP operands are specified, +the standard input shall be used. +.sp +.SH STDIN +.LP +The standard input shall be used only if no \fIfile\fP operands are +specified. See the INPUT FILES section. +.SH INPUT FILES +.LP +If the \fB-c\fP option is specified, the input file can contain arbitrary +data; otherwise, the input file shall be a text +file. +.SH ENVIRONMENT VARIABLES +.LP +The following environment variables shall affect the execution of +\fItail\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 and input files). +.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. +.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 +The designated portion of the input file shall be written to standard +output. +.SH STDERR +.LP +The standard error shall be used only for diagnostic messages. +.SH OUTPUT FILES +.LP +None. +.SH EXTENDED DESCRIPTION +.LP +None. +.SH EXIT STATUS +.LP +The following exit values shall be returned: +.TP 7 +\ 0 +Successful completion. +.TP 7 +>0 +An error occurred. +.sp +.SH CONSEQUENCES OF ERRORS +.LP +Default. +.LP +\fIThe following sections are informative.\fP +.SH APPLICATION USAGE +.LP +The \fB-c\fP 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. +.LP +Although the input file to \fItail\fP 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 IEEE\ Std\ 1003.1-2001. Since this +volume of IEEE\ Std\ 1003.1-2001 does not specify the block size used +when doing input, \fItail\fP need not read all of +the data from devices that only perform block transfers. +.SH EXAMPLES +.LP +The \fB-f\fP 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 +.nf + +\fBtail -f fred +\fP +.fi +.RE +.LP +prints the last ten lines of the file \fBfred\fP, followed by any +lines that are appended to \fBfred\fP between the time +\fItail\fP is initiated and killed. As another example, the command: +.sp +.RS +.nf + +\fBtail -f -c 15 fred +\fP +.fi +.RE +.LP +prints the last 15 bytes of the file \fBfred\fP, followed by any bytes +that are appended to \fBfred\fP between the time +\fItail\fP is initiated and killed. +.SH RATIONALE +.LP +This version of \fItail\fP was created to allow conformance to the +Utility Syntax Guidelines. The historical \fB-b\fP option +was omitted because of the general non-portability of block-sized +units of text. The \fB-c\fP option historically meant +"characters", but this volume of IEEE\ Std\ 1003.1-2001 indicates +that it means "bytes". This was selected to allow +reasonable implementations when multi-byte characters are possible; +it was not named \fB-b\fP to avoid confusion with the +historical \fB-b\fP. +.LP +The origin of counting both lines and bytes is 1, matching all widespread +historical implementations. +.LP +The restriction on the internal buffer is a compromise between the +historical System V implementation of 4096 bytes and the BSD +32768 bytes. +.LP +The \fB-f\fP 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. +.LP +Historical documentation indicates that \fItail\fP ignores the \fB-f\fP +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 \fB-f\fP flag +if a FIFO was named as the \fIfile\fP operand. Since the +\fB-f\fP option is not useful on pipes and all historical implementations +ignore \fB-f\fP if no \fIfile\fP operand is specified +and standard input is a pipe, this volume of IEEE\ Std\ 1003.1-2001 +requires this behavior. However, since the \fB-f\fP +option is useful on a FIFO, this volume of IEEE\ Std\ 1003.1-2001 +also requires that if standard input is a FIFO or a FIFO +is named, the \fB-f\fP option shall not be ignored. Although historical +behavior does not ignore the \fB-f\fP option for other +file types, this is unspecified so that implementations are allowed +to ignore the \fB-f\fP option if it is known that the file +cannot be extended. +.LP +This was changed to the current form based on comments noting that +\fB-c\fP was almost never used without specifying a number +and that there was no need to specify \fB-l\fP if \fB-n\fP \fInumber\fP +was given. +.SH FUTURE DIRECTIONS +.LP +None. +.SH SEE ALSO +.LP +\fIhead\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 . |