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.so man.macros
.HS Tcl_TildeSubst tclc 7.0
.BS
.SH NAME
Tcl_TildeSubst \- replace tilde with home directory in a file name
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
char *
.VS
\fBTcl_TildeSubst\fR(\fIinterp\fR, \fIname\fR, \fIbufferPtr)
.VE
.SH ARGUMENTS
.AS Tcl_DString *bufferPtr
.AP Tcl_Interp *interp in
Interpreter in which to report an error, if any.
.AP char *name in
File name, which may start with a ``~''.
.AP Tcl_DString *bufferPtr
.VS
If needed, this dynamic string is used to store the new file name.
At the time of the call it should be uninitialized or empty.  The
caller must eventually call \fBTcl_DStringFree\fR to free up
anything stored here.
.VE
.BE

.SH DESCRIPTION
.PP
This utility procedure does tilde substition.  If \fIname\fR doesn't
start with a ``~'' character, then the procedure returns \fIname\fR.
If \fIname\fR does start with a tilde, then \fBTcl_TildeSubst\fR
returns a new string identical to \fIname\fR except that the first
element of \fIname\fR is replaced with the location of the home
directory for the given user.  The substitution is carried out in
the same way that it would be done by \fIcsh\fR.  If the tilde is
followed immediately by a slash, then the \fB$HOME\fR environment
variable is substituted.  Otherwise the characters between the
tilde and the next slash are taken as a user name, which is
looked up in the password file;  the user's home directory is
retrieved from the password file and substituted.
.PP
If
.VS
\fBTcl_TildeSubst\fR has to do tilde substitution then it uses
the dynamic string at \fI*bufferPtr\fR to hold the new string it
generates.  After \fBTcl_TildeSubst\fR returns, the caller must
eventually invoke \fBTcl_DStringFree\fR to free up any information
placed in \fI*bufferPtr\fR.  The caller need not know whether or
not \fBTcl_TildeSubst\fR actually used the string;  \fBTcl_TildeSubst\fR
initializes \fI*bufferPtr\fR even if it doesn't use it, so the call to
\fBTcl_DStringFree\fR will be safe in either case.
.VE
.PP
If an error occurs (e.g. because there was no user by the given
name) then NULL is returned and an error message will be left
at \fIinterp->result\fR.  It is assumed that \fIinterp->result\fR
has been initialized in the standard way when \fBTcl_TildeSubst\fR
is invoked.

.SH KEYWORDS
file name, home directory, tilde, user