cpio(1) UNIX System V(Essential Utilities) cpio(1)
NAME
cpio - copy file archives in and out
SYNOPSIS
cpio -i[bBcdfkmrsStuvV6KT] [-C bufsize] [-E file] [-H hdr] [-I file [-M
message]] [-R ID]] [pattern . . . ]
cpio -o[aABcLvVKT] [-C bufsize] [-H hdr] [-O file [-M message]]
cpio -p[adlLmuvVKT] [-R ID]] directory
DESCRIPTION
The -i, -o, and -p options select the action to be performed. The
following list describes each of the actions (which are mutually
exclusive).
cpio -i (copy in) extracts files from the standard input, which is
assumed to be the product of a previous cpio -o. Only files with names
that match patterns are selected. patterns are regular expressions given
in the filename-generating notation of sh(1). In patterns, meta-
characters ?, *, and [ . . . ] match the slash (/) character, and
backslash (\) is an escape character. A ! meta-character means not.
(For example, the !abc* pattern would exclude all files that begin with
abc.) Multiple patterns may be specified and if no patterns are
specified, the default for patterns is * (that is, select all files).
Each pattern must be enclosed in double quotes; otherwise, the name of a
file in the current directory might be used. Extracted files are
conditionally created and copied into the current directory tree based on
the options described below. The permissions of the files will be those
of the previous cpio -o. Owner and group permissions will be the same as
the current user unless the current user is super-user. If this is true,
owner and group permissions will be the same as those resulting from the
previous cpio -o.
NOTE: If cpio -i tries to create a file that already exists and the
existing file is the same age or younger (newer), cpio will output a
warning message and not replace the file. (The -u option can be used to
overwrite, unconditionally, the existing file.) If file names are given
as absolute pathnames to cpio -o, then when the files are restored via
cpio -i, they will be written to their original directories regardless of
the current directory. This behavior can be circumvented by using the -r
option.
cpio -o (copy out) reads the standard input to obtain a list of path
names and copies those files onto the standard output together with path
name and status information.
cpio -p (pass) reads the standard input to obtain a list of path names of
files that are conditionally created and copied into the destination
directory tree based on the options described below.
10/89 Page 1
cpio(1) UNIX System V(Essential Utilities) cpio(1)
The meanings of the available options are
-a Reset access times of input files after they have been copied.
Access times are not reset for linked files when cpio -pla is
specified (mutually exclusive with -m).
-A Append files to an archive. The -A option requires the -O option.
Valid only with archives that are files, or that are on floppy
diskettes or hard disk partitions.
-b Reverse the order of the bytes within each word. (Use only with
the -i option.)
-B Input/output is to be blocked 5,120 bytes to the record. The
default buffer size is device dependent when this and the -C
options are not used.
-c Read or write header information in ASCII character form for
portability. Always use this option (or the -H option) when the
origin and the destination machines are different types (mutually
exclusive with -H and -6). (The -c option implies expanded device
numbers.)
-C bufsize
Input/output is to be blocked bufsize bytes to the record, where
bufsize is replaced by a positive integer. The default buffer size
is device dependent when this and -B options are not used.
-d Directories are to be created as needed.
-E file
Specify an input file (file) that contains a list of filenames to
be extracted from the archive (one filename per line).
-f Copy in all files except those in patterns. (See the paragraph on
cpio -i for a description of patterns.)
-H hdr
Read or write header information in hdr format. Always use this
option or the -c option when the origin and the destination
machines are different types (mutually exclusive with -c and -6).
Valid values for hdr are:
crc or CRC ASCII header with expanded device numbers and an
additional per-file checksum
ustar or USTAR IEEE/P1003 Data Interchange Standard header and
format
tar or TAR tar header and format
Page 2 10/89
cpio(1) UNIX System V(Essential Utilities) cpio(1)
odc ASCII header with small device numbers
-I file
Read the contents of file as an input archive. If file is a
character special device, and the current medium has been
completely read, replace the medium and press RETURN to continue to
the next medium. This option is used only with the -i option.
-k Attempt to skip corrupted file headers and I/O errors that may be
encountered. If you want to copy files from a medium that is
corrupted or out of sequence, this option lets you read only those
files with good headers. (For cpio archives that contain other
cpio archives, if an error is encountered cpio may terminate
prematurely. cpio will find the next good header, which may be one
for a smaller archive, and terminate when the smaller archive's
trailer is encountered.) Used only with the -i option.
-l Whenever possible, link files rather than copying them. (Usable
only with the -p option.)
-L Follow symbolic links. The default is not to follow symbolic
links.
-m Retain previous file modification time. This option is ineffective
on directories that are being copied (mutually exclusive with -a).
-M message
Define a message to use when switching media. When you use the -O
or -I options and specify a character special device, you can use
this option to define the message that is printed when you reach
the end of the medium. One %d can be placed in message to print
the sequence number of the next medium needed to continue.
-O file
Direct the output of cpio to file. If file is a character special
device and the current medium is full, replace the medium and press
RETURN to continue to the next medium. Use only with the -o
option.
-r Interactively rename files. If the user presses the RETURN key
alone, the file is skipped. If the user types a ``.'' the original
pathname will be retained. (Not available with cpio -p.)
-R ID Reassign ownership and group information for each file to user ID
(ID must be a valid user ID from /etc/passwd). This option is
valid only for the super-user.
-s Swap bytes within each half word.
-S Swap halfwords within each word.
10/89 Page 3
cpio(1) UNIX System V(Essential Utilities) cpio(1)
-t Print a table of contents of the input. No files are created
(mutually exclusive with -V).
-u Copy unconditionally (normally, an older file will not replace a
newer file with the same name).
-v Verbose: causes a list of file names to be printed. When used with
the -t option, the table of contents looks like the output of an ls
-l command [see ls(1)].
-V Special Verbose: print a dot for each file read or written.
Useful to assure the user that cpio is working without printing out
all file names.
-K 1K Blocks: force the blocking size to be a multiple of 1K.
-T Truncate: truncate long file names to 14 characters.
-6 Process a UNIX System Sixth Edition archive format file. Use only
with the -i option (mutually exclusive with -c and -H)).
NOTE: cpio assumes four-byte words.
If, when writing to a character device (-o) or reading from a character
device (-i), cpio reaches the end of a medium (such as the end of a
diskette), and the -O and -I options aren't used, cpio will print the
following message:
If you want to go on, type device/file name when ready.
To continue, you must replace the medium and type the character special
device name (/dev/rdsk/f0 for example) and press RETURN. You may want to
continue by directing cpio to use a different device. For example, if
you have two floppy drives you may want to switch between them so cpio
can proceed while you are changing the floppies. (Simply pressing RETURN
causes the cpio process to exit.)
EXAMPLES
The following examples show three uses of cpio.
When standard input is directed through a pipe to cpio -o, it groups the
files so they can be directed (>) to a single file (../newfile). The -c
option insures that the file will be portable to other machines (as would
the -H option). Instead of ls(1), you could use find(1), echo(1),
cat(1), and so on, to pipe a list of names to cpio. You could direct the
output to a device instead of a file.
ls | cpio -oc > ../newfile
cpio -i uses the output file of cpio -o (directed through a pipe with cat
in the example below), extracts those files that match the patterns
(memo/a1, memo/b*), creates directories below the current directory as
Page 4 10/89
cpio(1) UNIX System V(Essential Utilities) cpio(1)
needed (-d option), and places the files in the appropriate directories.
The -c option is used if the input file was created with a portable
header. If no patterns were given, all files from newfile would be
placed in the directory.
cat newfile | cpio -icd "memo/a1" "memo/b*"
cpio -p takes the file names piped to it and copies or links (-l option)
those files to another directory (newdir in the example below). The -d
option says to create directories as needed. The -m option says retain
the modification time. (It is important to use the -depth option of
find(1) to generate path names for cpio. This eliminates problems cpio
could have trying to create files under read-only directories.) The
destination directory, newdir, must exist.
find . -depth -print | cpio -pdlmv newdir
Note that when you use cpio in conjunction with find, if you use the -L
option with cpio then you must use the -follow option with find and vice
versa. Otherwise there will be undesirable results.
SEE ALSO
ar(1), cat(1), echo(1), find(1), ls(1), tar(1)
archives(4) in the System Administrator's Reference Manual
NOTES
An archive created with the -c option on a System V Release 4 system
cannot be read on System V Release 3.2 systems, or earlier. Use the -H
odc option, which is equivalent to the header created by the -c option in
earlier System V releases, if the cpio image will be read on a pre-System
V Release 4 system.
System V Releases prior to Release 4 do not recognize symbolic links.
The result of copying in a symbolic link on an older release will be a
regular file that contains the pathname of the referenced file.
Path names are restricted to 256 characters for the binary (the default)
and
-H odc header formats. Otherwise, path names are restricted to 1024
characters.
Only the super-user can copy special files.
Blocks are reported in 512-byte quantities.
If a file has 000 permissions, contains more than 0 characters of data,
and the user is not root, the file will not be saved or restored.
When attempting to redirect stdin or stdout from or to a character or
block special device (for example, /dev/diskette), an error message
``Cannot read from device'' or ``Cannot write to device,'' does not
necessarily indicate that a true I/O error has occurred. More likely,
10/89 Page 5
cpio(1) UNIX System V(Essential Utilities) cpio(1)
the user does not have access to that device, and should request that the
system administrator allocate that device for the user [see
admalloc(1M)].
Prior to Release 4, the default buffer size was 512 bytes. Beginning
with Release 4, the default buffer size is optimized for the device and
using the -C option to specify a different block size may cause cpio to
fail. Therefore, care must be taken when choosing the block size. For
example, for floppy disks, bufsize must be a multiple of 512 (one floppy
sector). To avoid wasting space on streaming tape drives, use the -C
option with an appropriate block size.
Page 6 10/89