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mktemp


NAME
     mktemp - make temporary filename

SYNOPSIS
     mktemp [-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 create a unique filename. See OPERANDS.


     The template is passed  to  mktemp(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 readable and writable by its  owner  (unless
     the  -u  flag is given) and the filename is printed to stan-
     dard output.


     mktemp allows shell scripts to safely use  temporary  files.
     Traditionally,  many shell scripts take the name of the pro-
     gram 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  guaran-
     tees 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 out-
                     put to go to standard error.


     -t              Generate a path rooted in a temporary direc-
                     tory.  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 for-
                     ward 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 can-
     not get a safe temporary 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 environment 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  creation  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.

EXIT STATUS
     The following exit values are returned:

     0    Successful completion.


     1    An error occurred.


ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWcsu                     |
    |_____________________________|_____________________________|
    | Interface Stability         | Evolving                    |
    |_____________________________|_____________________________|


SEE ALSO
     sh(1), 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).










Man pages from Solaris 10 Update 8. See docs.sun.com and www.oracle.com for further documentation and Solaris information.
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