45 lines
2.8 KiB
HTML
45 lines
2.8 KiB
HTML
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<HTML><HEAD><TITLE>Tcl Built-In Commands - read manual page</TITLE></HEAD><BODY>
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<H3><A NAME="M2">NAME</A></H3>
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read - Read from a channel
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<H3><A NAME="M3">SYNOPSIS</A></H3>
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<B>read </B>?<B>-nonewline</B>? <I>channelId</I><BR>
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<B>read </B><I>channelId numChars</I><BR>
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<H3><A NAME="M4">DESCRIPTION</A></H3>
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In the first form, the <B>read</B> command reads all of the data from
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<I>channelId</I> up to the end of the file.
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If the <B>-nonewline</B> switch is specified then the last character
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of the file is discarded if it is a newline.
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In the second form, the extra argument specifies how many characters to
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read. Exactly that many characters will be read and returned, unless
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there are fewer than <I>numChars</I> left in the file; in this case
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all the remaining characters are returned. If the channel is
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configured to use a multi-byte encoding, then the number of characters
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read may not be the same as the number of bytes read.
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<P>
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If <I>channelId</I> is in nonblocking mode, the command may not read as
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many characters as requested: once all available input has been read,
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the command will return the data that is available rather than
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blocking for more input. If the channel is configured to use a
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multi-byte encoding, then there may actually be some bytes remaining
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in the internal buffers that do not form a complete character. These
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bytes will not be returned until a complete character is available or
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end-of-file is reached.
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The <B>-nonewline</B> switch is ignored if the command returns
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before reaching the end of the file.
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<P>
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<B>Read</B> translates end-of-line sequences in the input into
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newline characters according to the <B>-translation</B> option
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for the channel.
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See the <B><A HREF="../TkCmd/fconfigure.htm">fconfigure</A></B> manual entry for a discussion on ways in
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which <B><A HREF="../TkCmd/fconfigure.htm">fconfigure</A></B> will alter input.
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<H3><A NAME="M5">SEE ALSO</A></H3>
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<B><A HREF="../TkCmd/file.htm">file</A></B>, <B><A HREF="../TkCmd/eof.htm">eof</A></B>, <B><A HREF="../TkCmd/fblocked.htm">fblocked</A></B>, <B><A HREF="../TkCmd/fconfigure.htm">fconfigure</A></B>
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<H3><A NAME="M6">KEYWORDS</A></H3>
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<A href="../Keywords/B.htm#blocking">blocking</A>, <A href="../Keywords/C.htm#channel">channel</A>, <A href="../Keywords/E.htm#end of line">end of line</A>, <A href="../Keywords/E.htm#end of file">end of file</A>, <A href="../Keywords/N.htm#nonblocking">nonblocking</A>, <A href="../Keywords/R.htm#read">read</A>, <A href="../Keywords/T.htm#translation">translation</A>, <A href="../Keywords/E.htm#encoding">encoding</A>
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<HR><PRE>
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<A HREF="../copyright.htm">Copyright</A> © 1993 The Regents of the University of California.
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<A HREF="../copyright.htm">Copyright</A> © 1994-1996 Sun Microsystems, Inc.
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<A HREF="../copyright.htm">Copyright</A> © 1995-1997 Roger E. Critchlow Jr.</PRE>
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</BODY></HTML>
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