➜ ~ echo -n 'admin' | md5sum 21232f297a57a5a743894a0e4a801fc3 - ➜ ~ md5sum -h md5sum: invalid option -- 'h' Try `md5sum --help' for more information. ➜ ~ md5sum --help Usage: md5sum [OPTION]... [FILE]... Print or check MD5 (128-bit) checksums. With no FILE, or when FILE is -, read standard input. -b, --binary read in binary mode -c, --check read MD5 sums from the FILEs and check them -t, --text read in text mode (default) Note: There is no difference between binary and text mode option on GNU system. The following three options are useful only when verifying checksums: --quiet don't print OK for each successfully verified file --status don't output anything, status code shows success -w, --warn warn about improperly formatted checksum lines --help display this help and exit --version output version information and exit The sums are computed as described in RFC 1321. When checking, the input should be a former output of this program. The default mode is to print a line with checksum, a character indicating type (`*' for binary, ` ' for text), and name for each FILE. Report md5sum bugs to bug-coreutils@gnu.org GNU coreutils home page: <http://www.gnu.org/software/coreutils/> General help using GNU software: <http://www.gnu.org/gethelp/> For complete documentation, run: info coreutils 'md5sum invocation'