cpio -- archiver to copy and back up files

cpio archiver to copy and back up files	Command

SYNOPSIS

cpio -o [-aBcHhNvyz] [-C blocksize] [-O file] [-V volpat]

cpio -i [-BbcdfHhmNrsStuvqy] [-C blocksize] [-I file] [-V volpat] [pattern ...]

cpio -p [-aBdlNmruv] directory

The cpio command manipulates files called cpio archives. A cpio archive is a concatenation of files and directories preceded by a header that gives the file name and other file system information. With cpio, you can create a new archive, extract the contents of an existing archive, list archive contents, and copy files from one directory to another.

Primary Options

The three forms of the command shown in the synopsis represent the main functions of cpio. Every call to cpio must specify one and only one of the following primary options:

-i

reads an existing archive (created with the -o option) from the standard input. Unless you specify the -t option, cpio -i extracts all files matching one or more of the given pattern arguments from the archive. Patterns are the same as those used by file name 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, using the list of files read from the standard input. Such a list might be produced by the ls or find commands. For example,

ls . | cpio -o >arch

uses ls to list the files of the current directory, then pipes this list as input to cpio. The resulting archive contains the contents of all the files, and is written to arch.

-p

copies the list of files read from standard input to the specified directory. You can use this option to copy entire file trees.

Secondary Options

Consult the synopsis lines to determine which of the following additional options can be applied with a particular primary option:

-a

resets the access time of each file that is accessed for copying 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 long word and bytes to be swapped within each 16-bit word of each extracted file. This facilitates the transfer of information between different CPU architectures. This is equivalent to specifying both the -s and -S options.

-C blocksize

sets the buffer size to a specified blocksize, 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 non-binary streams (such as some data communications links) and is highly recommended for moving data between different processors, such as between a UNIX system and a PC.

-d

forces the creation of necessary intermediate directories if 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.

-H

creates and reads cpio archives that contain extraneous header characters, for compatibility with historical versions of cpio.

-h

creates and reads cpio archives with headers structured in a "little-endian" pattern. The term "little-endian" refers to the internal ordering of bytes representing numbers, stipulating that the least significant values come first. This is the common standard for PCs, but is contrary to the "big-endian" standard of most UNIX machines.

The default for MKS cpio is "big-endian." For example, the 32-bit hexadecimal number 1234, written as a cpio header using the -h option, would be stored in "little-endian" order:

34 12

Without the -h option, cpio defaults to "big-endian" ordering:

12 34

MKS cpio automatically senses the byte ordering of any archive header being read, and prints a notification to standard output if byte reversal is present.

-I file

causes input to be read from the specified file, rather than standard input. The specified file may be the name of a device, for example, A:. cpio reads the raw disk for the cpio file.

-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 when the file is written. This option has no effect on directories.

-O file

causes output to be written to the specified file, rather than standard output. The specified file may be the name of a device, for example, A:, and writes the cpio file to the raw disk.

-q

assumes all created files are ASCII text. This means that any \r (carriage return) characters are stripped, and only the \n (newlines) are retained.

-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 long words 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. This option does not affect the headers.

-t

prevents file extraction, producing instead a table of file names 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 multi-volume support. cpio writes output to files whose names 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 press ENTER before it proceeds with the operation. cpio issues a similar 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, -y does not ask for a volume number to begin with, but does ask if cpio gets a read or write error.

-z

performs compression. Output is at compression level 5. On input, any compression level up to 9 is acceptable. In addition, -z expands compressed archives on input.

cpio uses the gzip format to compress files.

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.

EXAMPLES

To copy an entire diskette file system to the current directory, use

find a: -type f | cpio -pvd .

To archive the current directory onto diskette in a system-independent (portable) format:

find . -type f | cpio -ocO a:

To recover a directory from a portable archive diskette:

cpio -icdm -I a:

To archive a directory xx that may be larger than a single diskette, using compression:

find xx -type f | cpio -ocvzV a:#.cpz

DIAGNOSTICS

Possible exit status values are:

0

Successful completion.

1

Failure due to any of the following:

— an invalid option

— invalid command line arguments

— out of memory

— compression error

— failure on extraction

— failure on creation

PORTABILITY

x/OPEN Portability Guide 4.0.

We strongly recommend, however, that you specify tape devices as described under tape. For example

/dev/mt0

The -b, -C, -I, -O, -q, -S, -s, -V, -y, and -z options are extensions to the x/OPEN standard.

NOTES

When using its default binary method of storage, cpio cannot save files larger than two gigabytes in size in an archive. When storing archives in ASCII (because of -c), cpio cannot save files larger than eight gigabytes in size in an archive. However, other programs that extract files from cpio archives may be unable to properly extract files larger than two gigabytes and cpio issues a warning to that effect when you attempt to save such a file.

The -u option of cpio calls the sort utility. To ensure that this option works correctly, you should make certain that the MKS Toolkit sort utility (or one compatible with it) is the first one located by the command search path.

cpio

Command