167 lines
6.4 KiB
Groff
167 lines
6.4 KiB
Groff
'\"
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'\" Copyright (c) 1989-1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) SplitList.3 1.19 96/03/25 20:07:46
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'\"
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.so man.macros
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.TH Tcl_SplitList 3 7.4 Tcl "Tcl Library Procedures"
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.BS
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.SH NAME
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Tcl_SplitList, Tcl_Merge, Tcl_ScanElement, Tcl_ConvertElement \- manipulate Tcl lists
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.SH SYNOPSIS
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.nf
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\fB#include <tcl.h>\fR
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.sp
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int
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\fBTcl_SplitList\fR(\fIinterp, list, argcPtr, argvPtr\fR)
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.sp
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char *
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\fBTcl_Merge\fR(\fIargc, argv\fR)
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.sp
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int
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\fBTcl_ScanElement\fR(\fIsrc, flagsPtr\fR)
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.sp
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int
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\fBTcl_ConvertElement\fR(\fIsrc, dst, flags\fR)
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.SH ARGUMENTS
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.AS Tcl_Interp ***argvPtr
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.AP Tcl_Interp *interp out
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.VS
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Interpreter to use for error reporting. If NULL, then no error message
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is left.
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.VE
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.AP char *list in
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Pointer to a string with proper list structure.
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.AP int *argcPtr out
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Filled in with number of elements in \fIlist\fR.
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.AP char ***argvPtr out
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\fI*argvPtr\fR will be filled in with the address of an array of
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pointers to the strings that are the extracted elements of \fIlist\fR.
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There will be \fI*argcPtr\fR valid entries in the array, followed by
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a NULL entry.
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.AP int argc in
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Number of elements in \fIargv\fR.
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.AP char **argv in
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Array of strings to merge together into a single list.
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Each string will become a separate element of the list.
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.AP char *src in
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String that is to become an element of a list.
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.AP int *flagsPtr in
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Pointer to word to fill in with information about \fIsrc\fR.
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The value of *\fIflagsPtr\fR must be passed to \fBTcl_ConvertElement\fR.
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.AP char *dst in
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Place to copy converted list element. Must contain enough characters
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to hold converted string.
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.AP int flags in
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Information about \fIsrc\fR. Must be value returned by previous
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call to \fBTcl_ScanElement\fR, possibly OR-ed
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with \fBTCL_DONT_USE_BRACES\fR.
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.BE
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.SH DESCRIPTION
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.PP
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These procedures may be used to disassemble and reassemble Tcl lists.
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\fBTcl_SplitList\fR breaks a list up into its constituent elements,
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returning an array of pointers to the elements using
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\fIargcPtr\fR and \fIargvPtr\fR.
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While extracting the arguments, \fBTcl_SplitList\fR obeys the usual
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rules for backslash substitutions and braces. The area of
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memory pointed to by \fI*argvPtr\fR is dynamically allocated; in
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addition to the array of pointers, it
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also holds copies of all the list elements. It is the caller's
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responsibility to free up all of this storage.
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For example, suppose that you have called \fBTcl_SplitList\fR with
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the following code:
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.CS
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int argc, code;
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char *string;
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char **argv;
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\&...
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code = Tcl_SplitList(interp, string, &argc, &argv);
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.CE
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Then you should eventually free the storage with a call like the
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following:
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.CS
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free((char *) argv);
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.CE
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.PP
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\fBTcl_SplitList\fR normally returns \fBTCL_OK\fR, which means the list was
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successfully parsed.
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If there was a syntax error in \fIlist\fR, then \fBTCL_ERROR\fR is returned
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and \fIinterp->result\fR will point to an error message describing the
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.VS
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problem (if \fIinterp\fR was not NULL).
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.VE
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If \fBTCL_ERROR\fR is returned then no memory is allocated and \fI*argvPtr\fR
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is not modified.
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.PP
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\fBTcl_Merge\fR is the inverse of \fBTcl_SplitList\fR: it
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takes a collection of strings given by \fIargc\fR
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and \fIargv\fR and generates a result string
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that has proper list structure.
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This means that commands like \fBindex\fR may be used to
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extract the original elements again.
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In addition, if the result of \fBTcl_Merge\fR is passed to \fBTcl_Eval\fR,
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it will be parsed into \fIargc\fR words whose values will
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be the same as the \fIargv\fR strings passed to \fBTcl_Merge\fR.
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\fBTcl_Merge\fR will modify the list elements with braces and/or
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backslashes in order to produce proper Tcl list structure.
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The result string is dynamically allocated
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using \fBmalloc()\fR; the caller must eventually release the space
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using \fBfree()\fR.
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.PP
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If the result of \fBTcl_Merge\fR is passed to \fBTcl_SplitList\fR,
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the elements returned by \fBTcl_SplitList\fR will be identical to
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those passed into \fBTcl_Merge\fR.
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However, the converse is not true: if \fBTcl_SplitList\fR
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is passed a given string, and the resulting \fIargc\fR and
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\fIargv\fR are passed to \fBTcl_Merge\fR, the resulting string
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may not be the same as the original string passed to \fBTcl_SplitList\fR.
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This is because \fBTcl_Merge\fR may use backslashes and braces
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differently than the original string.
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.PP
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\fBTcl_ScanElement\fR and \fBTcl_ConvertElement\fR are the
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procedures that do all of the real work of \fBTcl_Merge\fR.
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\fBTcl_ScanElement\fR scans its \fIsrc\fR argument
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and determines how to use backslashes and braces
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when converting it to a list element.
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It returns an overestimate of the number of characters
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required to represent \fIsrc\fR as a list element, and
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it stores information in \fI*flagsPtr\fR that is needed
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by \fBTcl_ConvertElement\fR.
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.PP
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\fBTcl_ConvertElement\fR is a companion procedure to \fBTcl_ScanElement\fR.
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It does the actual work of converting a string to a list element.
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Its \fIflags\fR argument must be the same as the value returned
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by \fBTcl_ScanElement\fR.
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\fBTcl_ConvertElement\fR writes a proper list element to memory
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starting at *\fIdst\fR and returns a count of the total number
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of characters written, which will be no more than the result
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returned by \fBTcl_ScanElement\fR.
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\fBTcl_ConvertElement\fR writes out only the actual list element
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without any leading or trailing spaces: it is up to the caller to
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include spaces between adjacent list elements.
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.PP
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\fBTcl_ConvertElement\fR uses one of two different approaches to
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handle the special characters in \fIsrc\fR. Wherever possible, it
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handles special characters by surrounding the string with braces.
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This produces clean-looking output, but can't be used in some situations,
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such as when \fIsrc\fR contains unmatched braces.
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In these situations, \fBTcl_ConvertElement\fR handles special
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characters by generating backslash sequences for them.
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The caller may insist on the second approach by OR-ing the
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flag value returned by \fBTcl_ScanElement\fR with
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\fBTCL_DONT_USE_BRACES\fR.
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Although this will produce an uglier result, it is useful in some
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special situations, such as when \fBTcl_ConvertElement\fR is being
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used to generate a portion of an argument for a Tcl command.
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In this case, surrounding \fIsrc\fR with curly braces would cause
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the command not to be parsed correctly.
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.SH KEYWORDS
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backslash, convert, element, list, merge, split, strings
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