mktemp - Create a secure and uniquely named file or directory
mktemp [-dqt] [-p prefix_directory] [template]
Makes a directory instead of a file. Fails silently if an
error occurs. Prepends the specified path to the name
generated for the temporary file or directory.
This option implies the -t option. Therefore, the
value of the TMPDIR environment variable, if set,
overrides the path prefix specified by the -p
option. Creates a directory or file whose path
prefix is as follows (in highest to lowest order of
precedence): The value of the TMPDIR environment
variable The argument to the -p option /tmp
Specifies a template used by mktemp to form a unique name
for the file or directory being created. The template is a
combination of characters that are included in the name,
trailed by uppercase X characters (for example,
fpm.XXXXXXXX or fpmXXXXXX). When creating the name for
the file or directory, mktemp substitutes a random combination
of letters and numbers in place of the uppercase X
characters.
If the trailer contains fewer than six X characters,
mktemp increases the number of X characters
to six before substituting the random combination
of letters and numbers. However, in scripts that
might be ported to other platforms, specify at
least six X characters explicitly.
If template is omitted from the command, the value
tmp.XXXXXXXXXX is used, and the -t option is
implied.
When including both the template operand and the -t
option, template specifies the final component of
the path and cannot contain any slash (/) characters.
The mktemp utility is provided to give shell scripts a
safer way to create temporary files, particularly when
writing to world-writeable areas, such as /tmp or
/var/tmp. Traditional methods for creating temporary
files, such as combining the name of the program with the
process ID of the user running it, are highly predictable
and can allow system security to be compromised.
The mktemp utility creates a directory or file with a randomized
name and safe protection mode. In the event that
the generated name specifies an existing directory, regular
file, symbolic link, hard link, or fifo, the utility
automatically retries with a different name.
If mktemp is successful at generating a unique file name,
the file is created with mode 0600 and its name is written
to standard output. If mktemp is successful at generating
a unique directory name, the directory is created with
mode 0700 and its name is written to standard output.
The mktemp utility is derived from OpenBSD software.
Success. An error occurred.
The following diagnostics may be printed to standard error
during the normal course of utility operation. mktemp:
template must not contain directory separators in -t mode
If -t is included (or implied by the -p option),
template must specify only the final node of the
path.
This error is also returned if the -p option specifies
a directory that does not exist when the temporary
file is created. mktemp: cannot allocate
memory
Insufficient memory is available to the utility for
one of its operations. mktemp: path is too long
The length of the pathname for the generated file
exceeded PATH_MAX. mktemp: cannot make temporary
directory
The -d option was included and a directory could
not be created for one of the following reasons:
The utility could not generate a directory name
that is unique. An intermediate node in the specified
path does not exist. The process does not
have required permissions. Insufficient disk space
is available for directory creation. The maximum
number of inodes for the parent directory has been
reached. mktemp: cannot make temporary file
The file could not be created for one of the following
reasons: The utility could not generate a
file name that is unique. An intermediate node in
the specified path does not exist. The process
does not have required permissions. Insufficient
disk space is available for file creation. The
maximum number of inodes for the parent directory
has been reached.
The following example shows a simple use of mktemp in
which the template operand specifies the absolute path to
the temporary file and the script exits if it cannot create
the file:
TMPFILE=`/bin/mktemp /tmp/fpm.XXXXXX` if [ $? -ne 0
] then
echo "Cannot create temporary file; exiting..."
exit 1 fi
Because neither the -t nor -p option is included in
the command line, the value of TMPDIR cannot override
the file's path at run time.
When specifying the absolute path to the temporary
file, do not include $0 as shown in the following
example because $0 by itself sometimes represents
an absolute path:
TMPFILE=`/bin/mktemp /tmp/$0.XXXXXX`
Instead, include $0 along with basename as shown in
the following example:
TMPFILE=`/bin/mktemp /tmp/\`basename $0\`.XXXXXX`
The -t option in the following example allows the
utility to use the setting of the TMPDIR environment
variable (or, by default, /tmp) as the directory
prefix for the temporary file:
file_basename=`basename $0` TMPFILE=`mktemp -q -t
${file_basename}.XXXXXX` In the following example,
the -p option specifies a default temporary directory
other than /tmp; the temporary file will be
created in /extra/tmp unless the setting of the
TMPDIR environment variable at the time the script
runs overrides this path:
TMPFILE=`/bin/mktemp -p /extra/tmp fpm.XXXXXXXXXX`
Note that this example will cause the script to
fail if the /extra/tmp directory does not exist or
is not writeable when the utility attempts to create
the temporary file.
ENVIRONMENT VARIABLES [Toc] [Back] Provides a default value for the internationalization
variables that are unset or null. If LANG is unset or
null, the corresponding value from the default locale is
used. If any of the internationalization variables contain
an invalid setting, the utility behaves as if none of
the variables had been defined. If set to a non-empty
string value, overrides the values of all the other internationalization
variables. Determines the locale for the
format and contents of diagnostic messages written to
standard error. Determines the locale for interpreting
sequences of text data as characters (for example, as single-byte
or multibyte characters in operands and option
arguments). Determines the location of message catalogs
for the processing of LC_MESSAGES. Determines the directory
in which the temporary file is created when the -t
option is implicitly or explicitly specified.
Functions: mktemp(3)
Others: environ(5)
mktemp(1)
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