cpio — Copy in/out file archives
Format
cpio –o [ –aBcvyz] [–C blocksize] [–O file] [–V volpat]
cpio –i [–BbcdfmrsStuvqyz] [–C blocksize] [–I file]
[–V volpat] [pattern …]
cpio –p [–aBdlmruv] directory
The cpio utility is fully supported for compatibility with older UNIX systems. However, it is recommended that the pax utility be used instead because it may provide greater functionality and is considered the standard for portable UNIX applications as defined by POSIX.2 IEEE standard 1003.2-1992.
Description
cpio reads and writes files called cpio archives. A cpio archive is a concatenation of files and directories preceded by a header giving the filename and other file system information. With cpio, you can create a new archive, extract contents of an existing archive, list archive contents, and copy files from one directory to another.
Options
Every call to cpio must
specify one and only one of the following selector options:
- –i
- Reads an existing archive (created with the –o option) from the standard input (stdin). Unless you specify the –t option, cpio extracts all files matching one or more of the given pattern arguments from the archive. Patterns are the same as those used by filename generation (see sh). When you do not specify a pattern argument, the default pattern * is used; as a result, cpio extracts all files.
- –o
- Writes a new archive to the standard output (stdout), using
the list of files read from stdin. Such a list might be produced
by the ls or find commands.
For example:
uses ls to list the files of the working directory and then pipes this list as input to cpio. The resulting archive contains the contents of all the files, and is written to arch.ls . | cpio –o >arch - –p
- Is shorthand for:
where cpio –i is performed in the given directory. You can use this option to copy entire file trees.cpio –o | (cd directory; cpio –i)
Consult the syntax lines to determine which
of the following additional options can be applied with a particular
selector option:
- –a
- Resets the access time (of each file accessed for copying to the archive) to what it was before the copy took place.
- –B
- Uses buffers of 5120 bytes for input and output rather than the default 512-byte buffers.
- –b
- Causes 16-bit words to be swapped within each longword and bytes to be swapped within each 16-bit word of each extracted file. This facilitates the transfer of information between different processor architectures. This is equivalent to specifying both the –s and –S options.
- –C blocksize
- Sets the buffer size to a specified block size, rather than the default 512-byte buffers.
- –c
- Reads and writes header information in ASCII form. Normally, cpio writes the header information in a compact binary format. This option produces an archive more amenable to transfer through nonbinary streams (such as some data communication links) and is highly recommended for those moving data between different processors.
- –d
- Forces the creation of necessary intermediate directories when they do not already exist.
- –f
- Inverts the sense of pattern matching. More precisely, cpio extracts a file from the archive if and only if it does not match any of the pattern arguments.
- –I file
- Causes input to be read from the specified file, rather than from stdin.
- –l
- Gives permission to create a link to a file rather than making a separate copy.
- –m
- Resets the modification time of an output file to the modification time of the source file. Normally, when cpio copies data into a file, it sets the modification time of the file to the time at which the file is written. This option has no effect on directories.
- –O file
- Causes output to be written to the specified file, rather than to stdout.
- –q
- Assumes all created files are text. This means that any \r (carriage
return) characters are stripped, and only the \n (newlines)
are retained.
Do not use the –q option for converting text to a system-independent format, because that would require all files to be read twice.
- –r
- Lets you rename files as cpio works. When extracting, cpio displays the name of the component it is about to extract and gives you the chance to specify a name for the extracted file. If you enter . as the name, cpio processes the file or directory with no modification to the name. If you just press Enter, cpio skips the file.
- –S
- For portability reasons, swaps pairs of 16-bit words within longwords (a 32-bit or 64-bit word) only when extracting files. This option does not affect the headers.
- –s
- For portability reasons, swaps pairs of bytes within each 16-bit word only when extracting files. –s does not affect the headers.
- –t
- Prevents files extraction, producing instead a table of filenames contained in the archive. See the description of the –v option.
- –u
- Copies an archive file to a target file even if the target is newer than the archive. Normally, cpio does not copy the file.
- –V volpat
- Provides automatic multivolume support. cpio writes output to files, the names of which are formatted using volpat. The current volume number replaces any occurrence of # in volpat. When you invoke cpio with this option, it asks for the first number in the archive set, and waits for you to type the number and a carriage return before its precedes with the operation. cpio issues the same sort of message when a write error or read error occurs on the archive; the reasoning is that this kind of error means that cpio has reached the end of the volume and should go on to a new one.
- –v
- Provides more verbose information than usual. cpio prints the names of files as it extracts them from or adds them to archives. When you specify both –v and –t, cpio prints a table of files in a format similar to that produced by the ls –l command.
- –y
- When used with –V, does not ask for a volume number to begin with, but does ask if it gets a read or write error.
- –z
- Performs Lempel-Ziv compression. Output is always a 16-bit compression. On input, any compression up to 16-bit is acceptable.
Usage notes
- Use the pax command if you need to use multibyte patterns when searching for filenames.
- The POSIX 1003.1 standard defines formats for cpio archives that limit the UIDs and GIDs that can be stored to the maximum value of 262143. Values larger than this will not be properly restored.
- The byte and word swapping done by the –b, –S, and –s options is effective only for the file data written. With or without the –c option, header information is always written in a machine-invariant format.
Localization
cpio uses
the following localization environment variable:
- LANG
- LC_ALL
- LC_MESSAGES
- LC_SYNTAX
- NLSPATH
See Localization for more information.
Exit values
- 0
- Successful completion
- 1
- Failure due to any of the following:
- An incorrect option
- Incorrect command-line arguments
- Out of memory
- Compression error
- Failure on extraction
- Failure on creation
Portability
X/Open Portability Guide, non-Berkeley UNIX systems after Version 7.
The –q, –V, –y, and –z options are specific to the z/OS shell.
Related information
compress, cp, dd, find, ls, mv, pax, tar, cpio, uncompress
The pax file format description in File formats.