Overview
cksum calculates the CRC checksum and byte count of a specified file and outputs it to standard output. This value is used as an indicator to quickly check if the file's content has changed, and it is primarily used for integrity verification after file transfer.
Key Features
- CRC32 checksum calculation
- File byte count output
- File integrity verification
- Standard input processing capability
Main Options
The cksum command is very simple and takes file paths as arguments. Most Linux systems use the CRC32 algorithm by default, and no separate algorithm selection option is provided.
Basic Arguments
Information/Help
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Description:
`cksum` Executes the command.
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Usage Examples
Calculate Checksum for a Single File
cksum myfile.txtOutputs the CRC checksum and byte count for the specified file.
Calculate Checksums for Multiple Files
cksum file1.txt file2.txtCalculates and outputs the checksum for each of multiple files.
Calculate Checksum from Standard Input
echo "Hello Linux" | cksumCalculates the checksum of data passed through a pipe (|).
Save Checksum to a File
cksum myfile.txt > myfile.cksumRedirects the calculated checksum results to a file for saving.
Verify Integrity by Comparing with Saved Checksum
cksum myfile.txt | diff - myfile.cksumCompares the checksum of the current file with a previously saved checksum file to check for file modifications.
Tips & Notes
cksum is useful for file integrity verification, but for security purposes, it is recommended to use stronger hashing algorithms.
Comparison of cksum and Other Hashing Tools
- cksum (CRC32): Primarily used to detect accidental errors (corruption) that may occur during data transmission. Not suitable for cryptographic security.
- md5sum, sha1sum, sha256sum: More robust for detecting intentional tampering of files and widely used for cryptographic security purposes. They have much higher collision resistance than cksum.
Detecting File Content Changes
The cksum value changes if even a single byte of the file's content is modified, allowing for quick detection of whether the file has been altered. This is useful for verifying the integrity of backup files or checking for corruption in downloaded files.