Update cheatsheets

sha256sum

@@ -0,0 +1,33 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# sha256sum
+
+> Calculate SHA256 cryptographic checksums.
+> More information: <https://www.gnu.org/software/coreutils/manual/html_node/sha2-utilities.html>.
+
+- Calculate the SHA256 checksum for one or more 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}}`
+
+- Calculate a SHA256 checksum from `stdin`:
+
+`{{command}} | sha256sum`
+
+- Read a file of SHA256 sums and filenames 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 when verification fails, ignoring missing files:
+
+`sha256sum --ignore-missing --check --quiet {{path/to/file.sha256}}`