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198 lines
10 KiB
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<HTML><HEAD><TITLE>Tcl Built-In Commands - scan manual page</TITLE></HEAD><BODY>
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<DL>
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<DD><A HREF="scan.htm#M2" NAME="L1049">NAME</A>
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<DL><DD>scan - Parse string using conversion specifiers in the style of sscanf</DL>
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<DD><A HREF="scan.htm#M3" NAME="L1050">SYNOPSIS</A>
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<DL>
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<DD><B>scan </B><I>string format </I>?<I>varName varName ...</I>?
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</DL>
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<DD><A HREF="scan.htm#M4" NAME="L1051">INTRODUCTION</A>
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<DD><A HREF="scan.htm#M5" NAME="L1052">DETAILS ON SCANNING</A>
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<DL>
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<DD><A HREF="scan.htm#M6" NAME="L1053"><B>d</B></A>
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<DD><A HREF="scan.htm#M7" NAME="L1054"><B>o</B></A>
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<DD><A HREF="scan.htm#M8" NAME="L1055"><B>x</B></A>
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<DD><A HREF="scan.htm#M9" NAME="L1056"><B>u</B></A>
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<DD><A HREF="scan.htm#M10" NAME="L1057"><B>i</B></A>
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<DD><A HREF="scan.htm#M11" NAME="L1058"><B>c</B></A>
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<DD><A HREF="scan.htm#M12" NAME="L1059"><B>s</B></A>
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<DD><A HREF="scan.htm#M13" NAME="L1060"><B>e</B> or <B>f</B> or <B>g</B></A>
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<DD><A HREF="scan.htm#M14" NAME="L1061"><B>[</B><I>chars</I><B>]</B></A>
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<DD><A HREF="scan.htm#M15" NAME="L1062"><B>[^</B><I>chars</I><B>]</B></A>
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<DD><A HREF="scan.htm#M16" NAME="L1063"><B>n</B></A>
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</DL>
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<DD><A HREF="scan.htm#M17" NAME="L1064">DIFFERENCES FROM ANSI SSCANF</A>
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<DL>
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</DL>
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<DD><A HREF="scan.htm#M18" NAME="L1065">SEE ALSO</A>
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<DD><A HREF="scan.htm#M19" NAME="L1066">KEYWORDS</A>
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</DL><HR>
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<H3><A NAME="M2">NAME</A></H3>
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scan - Parse string using conversion specifiers in the style of sscanf
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<H3><A NAME="M3">SYNOPSIS</A></H3>
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<B>scan </B><I>string format </I>?<I>varName varName ...</I>?<BR>
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<H3><A NAME="M4">INTRODUCTION</A></H3>
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This command parses fields from an input string in the same fashion as the
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ANSI C <B>sscanf</B> procedure and returns a count of the number of
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conversions performed, or -1 if the end of the input string is reached
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before any conversions have been performed. <I>String</I> gives the input
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to be parsed and <I>format</I> indicates how to parse it, using <B>%</B>
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conversion specifiers as in <B>sscanf</B>. Each <I>varName</I> gives the
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name of a variable; when a field is scanned from <I>string</I> the result is
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converted back into a string and assigned to the corresponding variable.
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If no <I>varName</I> variables are specified, then <B>scan</B> works in an
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inline manner, returning the data that would otherwise be stored in the
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variables as a list. In the inline case, an empty string is returned when
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the end of the input string is reached before any conversions have been
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performed.
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<H3><A NAME="M5">DETAILS ON SCANNING</A></H3>
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<B>Scan</B> operates by scanning <I>string</I> and <I>format</I> together.
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If the next character in <I>format</I> is a blank or tab then it
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matches any number of white space characters in <I>string</I> (including
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zero).
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Otherwise, if it isn't a <B>%</B> character then it
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must match the next character of <I>string</I>.
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When a <B>%</B> is encountered in <I>format</I>, it indicates
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the start of a conversion specifier.
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A conversion specifier contains up to four fields after the <B>%</B>:
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a <B>*</B>, which indicates that the converted value is to be discarded
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instead of assigned to a variable; a XPG3 position specifier; a number
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indicating a maximum field width; and a conversion character.
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All of these fields are optional except for the conversion character.
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The fields that are present must appear in the order given above.
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<P>
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When <B>scan</B> finds a conversion specifier in <I>format</I>, it
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first skips any white-space characters in <I>string</I> (unless the
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specifier is <B>[</B> or <B>c</B>).
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Then it converts the next input characters according to the
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conversion specifier and stores the result in the variable given
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by the next argument to <B>scan</B>.
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<P>
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If the <B>%</B> is followed by a decimal number and a <B>$</B>, as in
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``<B>%2$d</B>'', then the variable to use is not taken from the next
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sequential argument. Instead, it is taken from the argument indicated
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by the number, where 1 corresponds to the first <I>varName</I>. If
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there are any positional specifiers in <I>format</I> then all of the
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specifiers must be positional. Every <I>varName</I> on the argument
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list must correspond to exactly one conversion specifier or an error
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is generated, or in the inline case, any position can be specified
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at most once and the empty positions will be filled in with empty strings.
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<P>
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The following conversion characters are supported:
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<P>
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<DL>
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<P><DT><A NAME="M6"><B>d</B></A><DD>
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The input field must be a decimal integer.
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It is read in and the value is stored in the variable as a decimal string.
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<P><DT><A NAME="M7"><B>o</B></A><DD>
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The input field must be an octal integer. It is read in and the
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value is stored in the variable as a decimal string.
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If the value exceeds MAX_INT (017777777777 on platforms using 32-bit
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integers), it will be truncated to a signed integer. Hence, 037777777777
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will appear as -1 on a 32-bit machine.
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<P><DT><A NAME="M8"><B>x</B></A><DD>
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The input field must be a hexadecimal integer. It is read in
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and the value is stored in the variable as a decimal string.
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If the value exceeds MAX_INT (0x7FFFFFFF on platforms using 32-bit
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integers), it will be truncated to a signed integer. Hence, 0xFFFFFFFF
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will appear as -1 on a 32-bit machine.
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<P><DT><A NAME="M9"><B>u</B></A><DD>
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The input field must be a decimal integer. The value is stored in the
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variable as an unsigned decimal integer string.
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<P><DT><A NAME="M10"><B>i</B></A><DD>
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The input field must be an integer. The base (i.e. decimal, octal, or
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hexadecimal) is determined in the same fashion as described in
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<B><A HREF="../TkCmd/expr.htm">expr</A></B>. The value is stored in the variable as a decimal string.
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<P><DT><A NAME="M11"><B>c</B></A><DD>
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A single character is read in and its binary value is stored in
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the variable as a decimal string.
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Initial white space is not skipped in this case, so the input
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field may be a white-space character.
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This conversion is different from the ANSI standard in that the
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input field always consists of a single character and no field
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width may be specified.
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<P><DT><A NAME="M12"><B>s</B></A><DD>
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The input field consists of all the characters up to the next
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white-space character; the characters are copied to the variable.
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<P><DT><A NAME="M13"><B>e</B> or <B>f</B> or <B>g</B></A><DD>
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The input field must be a floating-point number consisting
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of an optional sign, a string of decimal digits possibly
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containing a decimal point, and an optional exponent consisting
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of an <B>e</B> or <B>E</B> followed by an optional sign and a string of
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decimal digits.
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It is read in and stored in the variable as a floating-point string.
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<P><DT><A NAME="M14"><B>[</B><I>chars</I><B>]</B></A><DD>
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The input field consists of any number of characters in
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<I>chars</I>.
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The matching string is stored in the variable.
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If the first character between the brackets is a <B>]</B> then
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it is treated as part of <I>chars</I> rather than the closing
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bracket for the set.
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If <I>chars</I>
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contains a sequence of the form <I>a</I><B>-</B><I>b</I> then any
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character between <I>a</I> and <I>b</I> (inclusive) will match.
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If the first or last character between the brackets is a <B>-</B>, then
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it is treated as part of <I>chars</I> rather than indicating a range.
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<P><DT><A NAME="M15"><B>[^</B><I>chars</I><B>]</B></A><DD>
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The input field consists of any number of characters not in
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<I>chars</I>.
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The matching string is stored in the variable.
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If the character immediately following the <B>^</B> is a <B>]</B> then it is
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treated as part of the set rather than the closing bracket for
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the set.
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If <I>chars</I>
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contains a sequence of the form <I>a</I><B>-</B><I>b</I> then any
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character between <I>a</I> and <I>b</I> (inclusive) will be excluded
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from the set.
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If the first or last character between the brackets is a <B>-</B>, then
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it is treated as part of <I>chars</I> rather than indicating a range.
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<P><DT><A NAME="M16"><B>n</B></A><DD>
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No input is consumed from the input string. Instead, the total number
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of chacters scanned from the input string so far is stored in the variable.
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<P></DL>
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<P>
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The number of characters read from the input for a conversion is the
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largest number that makes sense for that particular conversion (e.g.
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as many decimal digits as possible for <B>%d</B>, as
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many octal digits as possible for <B>%o</B>, and so on).
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The input field for a given conversion terminates either when a
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white-space character is encountered or when the maximum field
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width has been reached, whichever comes first.
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If a <B>*</B> is present in the conversion specifier
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then no variable is assigned and the next scan argument is not consumed.
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<H3><A NAME="M17">DIFFERENCES FROM ANSI SSCANF</A></H3>
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The behavior of the <B>scan</B> command is the same as the behavior of
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the ANSI C <B>sscanf</B> procedure except for the following differences:
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<P>
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<DL>
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<P><DT>[1]<DD>
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<B>%p</B> conversion specifier is not currently supported.
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<P><DT>[2]<DD>
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For <B>%c</B> conversions a single character value is
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converted to a decimal string, which is then assigned to the
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corresponding <I>varName</I>;
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no field width may be specified for this conversion.
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<P><DT>[3]<DD>
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The <B>l</B>, <B>h</B>, and <B>L</B> modifiers are ignored; integer
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values are always converted as if there were no modifier present
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and real values are always converted as if the <B>l</B> modifier
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were present (i.e. type <B>double</B> is used for the internal
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representation).
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<P><DT>[4]<DD>
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If the end of the input string is reached before any conversions have been
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performed and no variables are given, and empty string is returned.
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<P></DL>
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<H3><A NAME="M18">SEE ALSO</A></H3>
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<B><A HREF="../TkCmd/format.htm">format</A></B>, <B>sscanf</B>
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<H3><A NAME="M19">KEYWORDS</A></H3>
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<A href="../Keywords/C.htm#conversion specifier">conversion specifier</A>, <A href="../Keywords/P.htm#parse">parse</A>, <A href="../Keywords/S.htm#scan">scan</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> © 2000 Scriptics Corporation.
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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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