cpio - macOS

Overview

cpio is a command-line tool used on macOS for managing archives of files. It can pack and unpack files into a variety of formats, such as binary, ASCII, and byte-swapped. Primarily, cpio is used for creating software packages, backups, and distributing a large number of files conveniently. It is especially effective when dealing with scripts or programs that need to archive or extract directories and manage file permissions accurately.

Syntax

The basic usage of the cpio command is:

cpio -o|--create [options] <name-list >archive
cpio -i|--extract [options] <archive
cpio -p|--pass-through [options] destination-directory <name-list

Where:

  • -o, --create: Create an archive.
  • -i, --extract: Extract files from an archive.
  • -p, --pass-through: Copy files from one directory to another.

Options/Flags

Here are some commonly used options and flags in cpio:

  • -o, --create: Creates an archive.
  • -i, --extract: Extracts files from an archive. Used with patterns to specify which files to extract.
  • -p, --pass-through: Directs file copying to another directory, useful for mirroring directories.
  • -v, --verbose: Provides a more verbose (detailed) output, showing files as they are processed.
  • -d, --make-directories: Creates missing directories as needed when extracting files.
  • -m, --preserve-modification-time: Preserves modification times when copying files.
  • -c: Use the older portable ASCII format for the archive.
  • -B: Increases the block size to 5120 bytes, used primarily for efficiency in tape backups.

Examples

Creating an Archive:

find . -type f | cpio -ov > myfiles.cpio

This command finds all files in the current directory and creates an archive named myfiles.cpio.

Extracting an Archive:

cpio -iv < myfiles.cpio

This extracts files from myfiles.cpio into the current directory, listing the filenames as they are extracted.

Copying Directories:

find . -type f | cpio -pvd newdir

This command finds files in the current directory and copies them to newdir, creating the directory if it does not exist.

Common Issues

  • File Permission Errors: When extracting files, users might encounter permission errors. Use sudo or adjust permissions accordingly.
  • Large File Management: When managing large sets of data, users may find cpio slow or resource-intensive. Consider using more efficient formats or splitting the archive into smaller parts.

Integration

cpio can be integrated with shell scripts or used in combination with other commands like find, xargs, and compression tools like gzip:

find . -name "*.txt" | cpio -ov | gzip > txtfiles.cpio.gz

This command archives all .txt files and compresses the archive, saving space.

  • tar: Another popular archiving tool, often used interchangeably with cpio for different use cases.
  • gzip/gunzip: Compression tools frequently used alongside cpio to compress or decompress archives.

For further reading on cpio, consult the GNU cpio manual or the macOS man pages (man cpio).