mktemp(1) User Commands mktemp(1)NAMEmktemp - make temporary filename
SYNOPSISmktemp [-dtqu] [-p directory] [template]
DESCRIPTION
The mktemp utility makes a temporary filename. To do this, mktemp takes
the specified filename template and overwrites a portion of it to cre‐
ate a unique filename. See OPERANDS.
The template is passed to mkdtemp(3C) for directories or mkstemp(3C)
for ordinary files.
If mktemp can successfully generate a unique filename, the file (or
directory) is created with file permissions such that it is only read‐
able and writable by its owner (unless the -u flag is given) and the
filename is printed to standard output.
mktemp allows shell scripts to safely use temporary files. Tradition‐
ally, many shell scripts take the name of the program with the PID as a
suffix and used that as a temporary filename. This kind of naming
scheme is predictable and the race condition it creates is easy for an
attacker to win. A safer, though still inferior approach is to make a
temporary directory using the same naming scheme. While this guarantees
that a temporary file is not subverted, it still allows a simple denial
of service attack. Use mktemp instead.
OPTIONS
The following options are supported:
-d Make a directory instead of a file.
-p directory Use the specified directory as a prefix when generating
the temporary filename. The directory is overridden by
the user's TMPDIR environment variable if it is set.
This option implies the -t flag.
-q Fail silently if an error occurs. This is useful if a
script does not want error output to go to standard
error.
-t Generate a path rooted in a temporary directory. This
directory is chosen as follows: If the user's TMPDIR
environment variable is set, the directory contained
therein is used. Otherwise, if the -p flag was given
the specified directory is used. If none of the above
apply, /tmp is used. In this mode, the template (if
specified) should be a directory component (as opposed
to a full path) and thus should not contain any forward
slashes.
-u Operate in unsafe mode. The temp file is unlinked
before mktemp exits. This is slightly better than
mktemp(3C), but still introduces a race condition. Use
of this option is discouraged.
OPERANDS
The following operands are supported:
template template can be any filename with one or more Xs appended
to it, for example /tmp/tfile.XXXXXX.
If template is not specified, a default of tmp.XXXXXX is
used and the -t flag is implied.
EXAMPLES
Example 1 Using mktemp
The following example illustrates a simple use of mktemp in a sh(1)
script. In this example, the script quits if it cannot get a safe tem‐
porary file.
TMPFILE=`mktemp /tmp/example.XXXXXX`
if [ -z "$TMPFILE" ]; then exit 1; fi
echo "program output" >> $TMPFILE
Example 2 Using mktemp to Support TMPDIR
The following example uses mktemp to support for a user's TMPDIR envi‐
ronment variable:
TMPFILE=`mktemp -t example.XXXXXX`
if [ -z "$TMPFILE" ]; then exit 1; fi
echo "program output" >> $TMPFILE
Example 3 Using mktemp Without Specifying the Name of the Temporary
File
The following example uses mktemp without specifying the name of the
temporary file. In this case the -t flag is implied.
TMPFILE=`mktemp`
if [ -z "$TMPFILE" ]; then exit 1; fi
echo "program output" >> $TMPFILE
Example 4 Using mktemp with a Default Temporary Directory Other than
/tmp
The following example creates the temporary file in /extra/tmp unless
the user's TMPDIR environment variable specifies otherwise:
TMPFILE=`mktemp -p /extra/tmp example.XXXXX`
if [ -z "$TMPFILE" ]; then exit 1; fi
echo "program output" >> $TMPFILE
Example 5 Using mktemp to Remove a File
The following example attempts to create two temporary files. If cre‐
ation of the second temporary file fails, mktemp removes the first file
before exiting:
TMP1=`mktemp -t example.1.XXXXXX`
if [ -z "$TMP1" ]; then exit 1; fi
TMP2=`mktemp -t example.2.XXXXXX`
if [ -z "$TMP2" ]; then
rm -f $TMP1
exit 1
fi
Example 6 Using mktemp
The following example does not exit if mktemp is unable to create the
file. That part of the script has been protected.
TMPFILE=`mktemp -q -t example.XXXXXX`
if [ ! -z "$TMPFILE" ]
then
# Safe to use $TMPFILE in this block
echo data > $TMPFILE
...
rm -f $TMPFILE
fi
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables
that affect the execution of mktemp with the -t option: TMPDIR.
TMPDIR Name a directory used for creating temporary files to over‐
ride system default; used by mktemp.
EXIT STATUS
The following exit values are returned:
0 Successful completion.
1 An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWcsu │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Committed │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOsh(1), mkdtemp(3C), mkstemp(3C), mktemp(3C), attributes(5), environ(5)NOTES
The mktemp utility appeared in OpenBSD 2.1. The Solaris implementation
uses only as many `Xs' as are significant for mktemp(3C) and
mkstemp(3C).
SunOS 5.10 9 Aug 2012 mktemp(1)