csum - Linux

Overview

csum is a versatile Linux command that calculates and verifies checksums for files and standard input. It can generate different checksum types, including CRC32, MD5, SHA1, and SHA256, enhancing the integrity and authenticity of data.

Syntax

csum [OPTIONS] [FILE]...
csum -r [OPTIONS] DIRECTORY

Options/Flags

  • -a, –algorithm ALG: Specify checksum algorithm (crc32, md5, sha1, sha256). Defaults to crc32.
  • -c, –check: Verify checksums stored in input files.
  • -e, –quiet: Suppress informational output.
  • -h, –help: Display help information.
  • -l, –list: Print checksums in a textual format (default).
  • -p, –pipe: Pipe standard input to csum.
  • -o, –output FILE: Save checksums to specified file.
  • -r, –recursive: Calculate checksums for all files in a directory recursively.
  • -s, –status: Print status information for each file.
  • -v, –verbose: Print additional information.
  • -w, –raw: Print checksums in a raw binary format.

Examples

Generate Checksums for Files

csum file1 file2 file3

Verify Checksums for Files

csum -c file1.crc file2.crc file3.crc

Calculate Checksums Recursively

csum -r directory

Pipe Checksums to Another Command

csum -p | grep sha256

Save Checksums to a File

csum -o checksums.txt file1 file2

Common Issues

No File Specified

If no files are provided, csum will process standard input instead.

Invalid Algorithm

If an invalid checksum algorithm is specified, csum will exit with an error message.

File Permission Denied

Ensure that you have appropriate file permissions to read or write the files being processed.

Integration

csum can be integrated with other commands for advanced tasks. For instance, you can use it to:

  • Verify the integrity of downloaded files using wget:
wget -O file http://example.com/file && csum -c file.crc
  • Compare checksums for file backups using rsync:
rsync -av --checksum=crc32 source/ destination/ && csum -c source/*crc

Related Commands

  • cksum: Calculates CRC32 checksums only.
  • md5sum: Calculates MD5 checksums only.
  • sha1sum: Calculates SHA1 checksums only.
  • sha256sum: Calculates SHA256 checksums only.