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Text processing and string manipulation

  • Converting standard input's text to uppercase:

    tr "[:lower:]" "[:upper:]"

  • Converting standard input's text to lowercase:

    tr "[:upper:]" "[:lower:]"

Universally unique identifiers (UUIDs)

  • Generating random UUIDs (i.e. UUID v4):

    uuidgen -r

  • Generating UUIDs based on the current date and time and on the local machine's MAC address (i.e. UUID v1):

    uuidgen -t

Verifying CDs and DVDs against source ISO images

The checksum for an ISO image can easily be calculated in the standard way:

sha256sum ISO_IMAGE_PATH

However, calculating a checksum of a CD or DVD using

sha256sum /dev/cdrom

usually does not produce the expected result due to trailing blank space on the disk. Instead, you should detect the exact size of the ISO image in bytes and then run the following:

dd if=/dev/cdrom bs=1 count=ISO_IMAGE_SIZE_BYTES | sha256sum

You can speed this up by finding a larger proper divisor of the size in bytes, such as 2048, 2324 or 2336, and then using that for the bs argument while dividing the count argument by the same number.