---
name: "TildeSubst"
section: "3tcl"
platform: "linux"
package: "tcl74-dev"
version: "7.4p3-5"
release: "Debian 1.3 (Bo)"
platforms: ["linux"]
url: "https://new.carta.tech/TildeSubst"
---

# TildeSubst(3tcl)

replace tilde with home directory in a file name

```

```

## NAME

Tcl\_TildeSubst - replace tilde with home directory in a file name

## SYNOPSIS

```
#include <tcl.h>

char *
Tcl_TildeSubst(interp, name, bufferPtr)
```

## ARGUMENTS

- Tcl\_Interp *\*interp* (in)

  Interpreter in which to report an error, if any.

- char *\*name* (in)

  File name, which may start with a \`\`~''.

- Tcl\_DString *\*bufferPtr*

  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 **Tcl\_DStringFree** to free up anything stored here.

  ```

  ```

## DESCRIPTION

This utility procedure does tilde substitution.  If *name* doesn't start with a \`\`~'' character, then the procedure returns *name*. If *name* does start with a tilde, then **Tcl\_TildeSubst** returns a new string identical to *name* except that the first element of *name* 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 *csh*.  If the tilde is followed immediately by a slash, then the **$HOME** 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.

If **Tcl\_TildeSubst** has to do tilde substitution then it uses the dynamic string at *\*bufferPtr* to hold the new string it generates. After **Tcl\_TildeSubst** returns a non-NULL result, the caller must eventually invoke **Tcl\_DStringFree** to free up any information placed in *\*bufferPtr*.  The caller need not know whether or not **Tcl\_TildeSubst** actually used the string;  **Tcl\_TildeSubst** initializes *\*bufferPtr* even if it doesn't use it, so the call to **Tcl\_DStringFree** will be safe in either case.

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 *interp-\>result*. When an error occurs, **Tcl\_TildeSubst** frees the dynamic string itself so that the caller need not call **Tcl\_DStringFree**.

The caller is responsible for making sure that *interp-\>result* has its default empty value when **Tcl\_TildeSubst** is invoked.

## KEYWORDS

file name, home directory, tilde, user