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# AUTHOR <EMAIL@ADDRESS>, YEAR.
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"Project-Id-Version: 0\n"
"POT-Creation-Date: 2013-03-12T03:19:45\n"
"PO-Revision-Date: 2013-03-12T03:19:45\n"
"Last-Translator: Automatically generated\n"
"Language-Team: None\n"
"MIME-Version: 1.0\n"
"Content-Type: application/x-publican; charset=UTF-8\n"
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#. Tag: title
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msgid "Temporary files"
msgstr ""

#. Tag: para
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msgid "In this chapter, we describe how to create temporary files and directories, how to remove them, and how to work with programs which do not create files in ways that a safe with a shared directory for temporary files. General file system manipulation is treated in a separate chapter, <xref linkend=\"chap-Defensive_Coding-Tasks-File_System\" />."
msgstr ""

#. Tag: para
#, no-c-format
msgid "Secure creation of temporary files has four different aspects."
msgstr ""

#. Tag: para
#, no-c-format
msgid "The location of the directory for temporary files must be obtained in a secure manner (that is, untrusted environment variables must be ignored, see <xref linkend=\"sect-Defensive_Coding-Tasks-secure_getenv\" />)."
msgstr ""

#. Tag: para
#, no-c-format
msgid "A new file must be created. Reusing an existing file must be avoided (the <filename class=\"directory\">/tmp</filename> race condition). This is tricky because traditionally, system-wide temporary directories shared by all users are used."
msgstr ""

#. Tag: para
#, no-c-format
msgid "The file must be created in a way that makes it impossible for other users to open it."
msgstr ""

#. Tag: para
#, no-c-format
msgid "The descriptor for the temporary file should not leak to subprocesses."
msgstr ""

#. Tag: para
#, no-c-format
msgid "All functions mentioned below will take care of these aspects."
msgstr ""

#. Tag: para
#, no-c-format
msgid "Traditionally, temporary files are often used to reduce memory usage of programs. More and more systems use RAM-based file systems such as <literal>tmpfs</literal> for storing temporary files, to increase performance and decrease wear on Flash storage. As a result, spooling data to temporary files does not result in any memory savings, and the related complexity can be avoided if the data is kept in process memory."
msgstr ""

#. Tag: title
#, no-c-format
msgid "Obtaining the location of temporary directory"
msgstr ""

#. Tag: para
#, no-c-format
msgid "Some functions below need the location of a directory which stores temporary files. For C/C++ programs, use the following steps to obtain that directory:"
msgstr ""

#. Tag: para
#, no-c-format
msgid "Use <function>secure_getenv</function> to obtain the value of the <literal>TMPDIR</literal> environment variable. If it is set, convert the path to a fully-resolved absolute path, using <literal>realpath(path, NULL)</literal>. Check if the new path refers to a directory and is writeable. In this case, use it as the temporary directory."
msgstr ""

#. Tag: para
#, no-c-format
msgid "Fall back to <filename class=\"directory\">/tmp</filename>."
msgstr ""

#. Tag: para
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msgid "In Python, you can use the <varname>tempfile.tempdir</varname> variable."
msgstr ""

#. Tag: para
#, no-c-format
msgid "Java does not support SUID/SGID programs, so you can use the <function>java.lang.System.getenv(String)</function> method to obtain the value of the <literal>TMPDIR</literal> environment variable, and follow the two steps described above. (Java's default directory selection does not honor <literal>TMPDIR</literal>.)"
msgstr ""

#. Tag: title
#, no-c-format
msgid "Named temporary files"
msgstr ""

#. Tag: para
#, no-c-format
msgid "The <function>mkostemp</function> function creates a named temporary file. You should specify the <literal>O_CLOEXEC</literal> flag to avoid file descriptor leaks to subprocesses. (Applications which do not use multiple threads can also use <function>mkstemp</function>, but libraries should use <function>mkostemp</function>.) For determining the directory part of the file name pattern, see <xref linkend=\"chap-Defensive_Coding-Tasks-Temporary_Files-Location\" />."
msgstr ""

#. Tag: para
#, no-c-format
msgid "The file is not removed automatically. It is not safe to rename or delete the file before processing, or transform the name in any way (for example, by adding a file extension). If you need multiple temporary files, call <function>mkostemp</function> multiple times. Do not create additional file names derived from the name provided by a previous <function>mkostemp</function> call. However, it is safe to close the descriptor returned by <function>mkostemp</function> and reopen the file using the generated name."
msgstr ""

#. Tag: para
#, no-c-format
msgid "The Python class <literal>tempfile.NamedTemporaryFile</literal> provides similar functionality, except that the file is deleted automatically by default. Note that you may have to use the <literal>file</literal> attribute to obtain the actual file object because some programming interfaces cannot deal with file-like objects. The C function <function>mkostemp</function> is also available as <function>tempfile.mkstemp</function>."
msgstr ""

#. Tag: para
#, no-c-format
msgid "In Java, you can use the <function>java.io.File.createTempFile(String, String, File)</function> function, using the temporary file location determined according to <xref linkend=\"chap-Defensive_Coding-Tasks-Temporary_Files-Location\" />. Do not use <function>java.io.File.deleteOnExit()</function> to delete temporary files, and do not register a shutdown hook for each temporary file you create. In both cases, the deletion hint cannot be removed from the system if you delete the temporary file prior to termination of the VM, causing a memory leak."
msgstr ""

#. Tag: title
#, no-c-format
msgid "Temporary files without names"
msgstr ""

#. Tag: para
#, no-c-format
msgid "The <function>tmpfile</function> function creates a temporary file and immediately deletes it, while keeping the file open. As a result, the file lacks a name and its space is deallocated as soon as the file descriptor is closed (including the implicit close when the process terminates). This avoids cluttering the temporary directory with orphaned files."
msgstr ""

#. Tag: para
#, no-c-format
msgid "Alternatively, if the maximum size of the temporary file is known beforehand, the <function>fmemopen</function> function can be used to create a <literal>FILE *</literal> object which is backed by memory."
msgstr ""

#. Tag: para
#, no-c-format
msgid "In Python, unnamed temporary files are provided by the <literal>tempfile.TemporaryFile</literal> class, and the <literal>tempfile.SpooledTemporaryFile</literal> class provides a way to avoid creation of small temporary files."
msgstr ""

#. Tag: para
#, no-c-format
msgid "Java does not support unnamed temporary files."
msgstr ""

#. Tag: title
#, no-c-format
msgid "Temporary directories"
msgstr ""

#. Tag: para
#, no-c-format
msgid "The <function>mkdtemp</function> function can be used to create a temporary directory. (For determining the directory part of the file name pattern, see <xref linkend=\"chap-Defensive_Coding-Tasks-Temporary_Files-Location\" />.) The directory is not automatically removed. In Python, this function is available as <function>tempfile.mkdtemp</function>. In Java 7, temporary directories can be created using the <function>java.nio.file.Files.createTempDirectory(Path, String, FileAttribute...)</function> function."
msgstr ""

#. Tag: para
#, no-c-format
msgid "When creating files in the temporary directory, use automatically generated names, e.g., derived from a sequential counter. Files with externally provided names could be picked up in unexpected contexts, and crafted names could actually point outside of the tempoary directory (due to <emphasis>directory traversal</emphasis>)."
msgstr ""

#. Tag: para
#, no-c-format
msgid "Removing a directory tree in a completely safe manner is complicated. Unless there are overriding performance concerns, the <application>rm</application> program should be used, with the <option>-rf</option> and <option>--</option> options."
msgstr ""

#. Tag: title
#, no-c-format
msgid "Compensating for unsafe file creation"
msgstr ""

#. Tag: para
#, no-c-format
msgid "There are two ways to make a function or program which excepts a file name safe for use with temporary files. See <xref linkend=\"sect-Defensive_Coding-Tasks-Processes-Creation\" />, for details on subprocess creation."
msgstr ""

#. Tag: para
#, no-c-format
msgid "Create a temporary directory and place the file there. If possible, run the program in a subprocess which uses the temporary directory as its current directory, with a restricted environment. Use generated names for all files in that temporary directory. (See <xref linkend=\"chap-Defensive_Coding-Tasks-Temporary_Directory\" />.)"
msgstr ""

#. Tag: para
#, no-c-format
msgid "Create the temporary file and pass the generated file name to the function or program. This only works if the function or program can cope with a zero-length existing file. It is safe only under additional assumptions:"
msgstr ""

#. Tag: para
#, no-c-format
msgid "The function or program must not create additional files whose name is derived from the specified file name or are otherwise predictable."
msgstr ""

#. Tag: para
#, no-c-format
msgid "The function or program must not delete the file before processing it."
msgstr ""

#. Tag: para
#, no-c-format
msgid "It must not access any existing files in the same directory."
msgstr ""

#. Tag: para
#, no-c-format
msgid "It is often difficult to check whether these additional assumptions are matched, therefore this approach is not recommended."
msgstr ""

