cheat:sha256sum
---
tags: [ cryptography, hash, checksum, verification ]
---
# To compute hash (checksum) of <file>:
sha256sum <file>
# To compute hash (checksum) from input text:
# Enter text in keyboard and finish by ctrl-D at beginning of line
sha256sum
Some text
^D
echo -n "Hello World" | sha256sum
# To verify if a hash (checksum) is correct if a hash-file is provided:
# sha256sum will go thru the files listed in <file-with-list-of-checksums>.
# For each file it will look if it exists. If not, it will print an error.
# If it does exist it will compute the checksum and compare it with the hash
# provided in the <file-with-list-of-checksums>. If they match (good!) it
# will print "filename: OK".
# If they don't match (warning, you might have been hacked), it will
# print "filename: FAILED".
sha256sum --check <file-with-list-of-checksums>
# Same as above (but ignore missing files):
# This tells you if your file is an exact copy (OK) or has been
# tampered with (FAILED) without bothering you with warnings about
# missing files
sha256sum --check --ignore-missing <file-with-list-of-checksums>
tldr:sha256sum
# sha256sum
# Calculate SHA256 cryptographic checksums.
# More information: <https://www.gnu.org/software/coreutils/manual/html_node/sha2-utilities.html>.
# Calculate the SHA256 checksum for a file:
sha256sum path/to/file
# Calculate SHA256 checksums for multiple files:
sha256sum path/to/file1 path/to/file2
# Calculate and save the list of SHA256 checksums to a file:
sha256sum path/to/file1 path/to/file2 > path/to/file.sha256
# Read a file of SHA256 sums and verify all files have matching checksums:
sha256sum --check path/to/file.sha256
# Only show a message for missing files or when verification fails:
sha256sum --check --quiet path/to/file.sha256
# Only show a message for files for which verification fails, ignoring missing files:
sha256sum --ignore-missing --check --quiet path/to/file.sha256
$
cheat.sh