| 1 | '\" |
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| 2 | '\" Copyright (c) 1993 The Regents of the University of California. |
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| 3 | '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. |
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| 4 | '\" |
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| 5 | '\" See the file "license.terms" for information on usage and redistribution |
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| 6 | '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. |
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| 7 | '\" |
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| 8 | '\" RCS: @(#) $Id: gets.n,v 1.8 2005/05/10 18:34:00 kennykb Exp $ |
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| 9 | '\" |
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| 10 | .so man.macros |
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| 11 | .TH gets n 7.5 Tcl "Tcl Built-In Commands" |
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| 12 | .BS |
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| 13 | '\" Note: do not modify the .SH NAME line immediately below! |
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| 14 | .SH NAME |
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| 15 | gets \- Read a line from a channel |
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| 16 | .SH SYNOPSIS |
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| 17 | \fBgets \fIchannelId\fR ?\fIvarName\fR? |
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| 18 | .BE |
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| 19 | |
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| 20 | .SH DESCRIPTION |
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| 21 | .PP |
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| 22 | This command reads the next line from \fIchannelId\fR, returns everything |
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| 23 | in the line up to (but not including) the end-of-line character(s), and |
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| 24 | discards the end-of-line character(s). |
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| 25 | .PP |
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| 26 | \fIChannelId\fR must be an identifier for an open channel such as the |
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| 27 | Tcl standard input channel (\fBstdin\fR), the return value from an |
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| 28 | invocation of \fBopen\fR or \fBsocket\fR, or the result of a channel |
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| 29 | creation command provided by a Tcl extension. The channel must have |
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| 30 | been opened for input. |
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| 31 | .PP |
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| 32 | If \fIvarName\fR is omitted the line is returned as the result of the |
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| 33 | command. |
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| 34 | If \fIvarName\fR is specified then the line is placed in the variable by |
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| 35 | that name and the return value is a count of the number of characters |
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| 36 | returned. |
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| 37 | .PP |
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| 38 | If end of file occurs while scanning for an end of |
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| 39 | line, the command returns whatever input is available up to the end of file. |
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| 40 | If \fIchannelId\fR is in nonblocking mode and there is not a full |
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| 41 | line of input available, the command returns an empty string and |
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| 42 | does not consume any input. |
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| 43 | If \fIvarName\fR is specified and an empty string is returned in |
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| 44 | \fIvarName\fR because of end-of-file or because of insufficient |
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| 45 | data in nonblocking mode, then the return count is -1. |
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| 46 | Note that if \fIvarName\fR is not specified then the end-of-file |
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| 47 | and no-full-line-available cases can |
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| 48 | produce the same results as if there were an input line consisting |
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| 49 | only of the end-of-line character(s). |
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| 50 | The \fBeof\fR and \fBfblocked\fR commands can be used to distinguish |
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| 51 | these three cases. |
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| 52 | .SH "EXAMPLE" |
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| 53 | This example reads a file one line at a time and prints it out with |
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| 54 | the current line number attached to the start of each line. |
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| 55 | .PP |
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| 56 | .CS |
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| 57 | set chan [open "some.file.txt"] |
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| 58 | set lineNumber 0 |
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| 59 | while {[\fBgets\fR $chan line] >= 0} { |
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| 60 | puts "[incr lineNumber]: $line" |
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| 61 | } |
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| 62 | close $chan |
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| 63 | .CE |
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| 64 | |
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| 65 | .SH "SEE ALSO" |
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| 66 | file(n), eof(n), fblocked(n), Tcl_StandardChannels(3) |
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| 67 | |
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| 68 | .SH KEYWORDS |
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| 69 | blocking, channel, end of file, end of line, line, nonblocking, read |
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