NAME

cpio − copy file archives in and out

SYNOPSIS

cpio −o[acBv]

cpio −i[BcdmrtuvfsSb6] [ patterns ]

cpio −p[adlmuv] directory

DESCRIPTION

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.  Output is padded to a 512-byte boundary. 

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 name-generating notation of sh(1). In patterns, meta-characters ?, ∗, and [...] match the slash / character.  Multiple patterns may be specified and if no patterns are specified, the default for patterns is ∗ (i.e., select all files).  Each pattern should be surrounded by double quotes.  The extracted files are conditionally created and copied into the current directory tree based upon the options described below.  The permissions of the files will be those of the previous cpio −o.  The owner and group of the files will be that of the current user unless the user is super-user, which causes cpio to retain the owner and group of the files of 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 newer, cpio will output a warning message and not replace the file.  (The -u option can be used to unconditionally overwrite the existing file.) 

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 upon the options described below. 

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. 

B Input/output is to be blocked 5,120 bytes to the record (does not apply to the pass option; meaningful only with data directed to or from a character special device, e.g. /dev/rmt/0m. 

d Directories are to be created as needed. 

c Write header information in ASCII character form for portability.  Always use this option when origin and destination machines are different types. 

r Interactively rename files.  If the user types a null line, the file is skipped. (Not available with cpio -p.) 

t Print a table of contents of the input.  No files are created. 

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)).

l Whenever possible, link files rather than copying them.  Usable only with the −p option. 

m Retain previous file modification time.  This option is ineffective on directories that are being copied. 

f Copy in all files except those in patterns.

s Swap bytes within each half word.  Use only with the −i option. 

S Swap halfwords within each word.  Use only with the −i option. 

b Reverses the order of the bytes within each word.  Use only with the −i option. 

6 Process an old (i.e. UNIX System Sixth Edition format) file.  Only useful with -i (copy in). 

NOTE: cpio assumes four-byte words. 

If cpio reaches end of medium (end of a diskette for example), when writing to (-o) or reading from (-i) a character special device, cpio will print the 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/rtape/c0d6h for example) and carriage 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.  (A carriage return alone 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).  Instead of "ls," you could use find, echo, cat, etc. to pipe a list of names to cpio.  You could direct the output to a device instead of a file. 

ls │ cpio −o >../newfile

cpio −i uses the output file of cpio −o (directed through a pipe with cat in the example), takes out those files that match the patterns (memo/a1, memo/b∗), creates directories below the current directory as needed (-d option), and places the files in the appropriate directories.  If no patterns were given, all files from "newfile" would be placed in the directory. 

cat newfile │ cpio −id "memo/a1" "memo/b∗"

cpio −p takes the file names piped to it and copies or links (-l option) those files to another directory on your machine (newdir in the example).  The -d options says to create directories as needed.  The −m option says retain the modification time.  (It is important to use the -depth option of find to generate path names for cpio.  This eliminates problems cpio could have trying to create files under read-only directories.) 

find . −depth −print │ cpio −pdlmv newdir

SEE ALSO

ar(1), find(1), ls(1), tar(1), cpio(4). 

NOTES

1) Path names are restricted to 256 characters.
2) Only the super-user can copy special files.
3) Blocks are reported in 512-byte quantities.

September 29, 2021