.\" -*-nroff-*-
.TH tmpdir 1 "6 April 1999" "Local tools"
.SH NAME
tmpdir \- choose, or check a choice of, temporary directory
.SH SYNOPSIS
.B tmpdir
.RB [ \-bcv ]
.RB [ \-g
.IR group ]
.RB [ \-C
.IR dir ]
.SH USAGE
The
.B tmpdir
program creates a secure place for temporary files to be stored, and
outputs an assignment to the
.B TMPDIR
variable suitable for execution by a shell.
.PP
Many programs aren't sufficiently careful about how they handle
temporary files.  For example, if a program which creates files in
.B /tmp
without making careful checks beforehand, a malicious user who can
predict the name that the program will use can create a symbolic link
with that name: when run, the program will then overwrite some file
using your current privileges.  Similarly, many programs create
temporary files using generous default permissions, which may well be a
mistake.
.PP
The
.B tmpdir
program finds a secure place for temporary files, creating one if
necessary.  The criteria it uses to choose a place are as follows:
.IP "   1."
The temporary directory must be owned by the user, and have mode 700
(i.e., readable, writable and searchable only by the owner).
.IP "   2."
The path through the filesystem to the temporary directory must be
secure against modifications by other malicious users.  See the
.BR chkpath (1)
manual page for a description of how this is done: the two programs work
in the same way.
.PP
First,
.B tmpdir
checks to see whether the current value of the
.B TMPDIR
environment variable is a secure place for temporary files.  If so, it
is accepted immediately.  Otherwise, it tries to find or create a
directory in
.B /tmp
(on the assumption that this is a fast disk suitable for temporary
files), with the name
.BI /tmp/ user \- suffix
for some
.IR suffix .
If that fails, it tries to create a directory in your home directory,
with the name
.BI ~/tmp\- suffix\fR.
If
.I that
fails too, then
.B tmpdir
gives up: if your home directory's not secure (or full) than a secure
temporary directory is the least of your worries.
.SS Options
The following options are supported:
.TP
.B "\-b, \-\-bourne"
Output an assignment using Bourne shell syntax.  The default is to
examine the user's shell and decide which syntax to use based on that.
.TP
.B "\-c, \-\-cshell"
Output an assignment using C shell syntax.
.TP
.BI "\-g, \-\-group " group
Trust (the members of)
.IR group :
consider directories they can write to be safe.
.TP
.B "-v, \-\-verbose"
Report problems to standard error.  Repeat for more verbosity.
.TP
.BI "\-C, --check " dir
Don't try to find a temporary directory; just see whether
.I dir
is secure, and exit successfully if it is (and unsuccessfully if it
isn't).
.SH BUGS
None known.
.SH SEE ALSO
.BR chkpath (1),
.BR checkpath (3),
.BR tmpnam (3),
.BR tmpfile (3).
.SH AUTHOR
Mark Wooding (mdw@nsict.org).