在mac系统中，自带的有命令md5 可以帮我们计算文件或者字符串的md5值， shasum命令可以帮我们计算文件sha值。 其使用方法如下：
md5 命令
语法： md5 [-pqrtx] [-s string] [file ...]
ps: 在unix类系统的命令语法中，中括号[] 中的表示可选项，这个是默认的公用规范，必须要学会！！
计算字符串md5
➜ ~ md5 -s admin
MD5 ("admin") = 21232f297a57a5a743894a0e4a801fc3计算文件md5
➜ ~ md5 yourfile.txt
MD5 (yourfile.txt) = 7b4b08855739c05400155d5a3445be78md5命令选项
-s string
Print a checksum of the given string.
-p Echo stdin to stdout and append the checksum to stdout.
-q Quiet mode - only the checksum is printed out. Overrides the -r
option.
-r Reverses the format of the output. This helps with visual diffs.
Does nothing when combined with the -ptx options.
-t Run a built-in time trial.
-x Run a built-in test script.
shasum命令
计算文件hash 支持的sha算法有 224, 256, 384, 512, 512224, 512256
➜ ~ shasum -a 256 yourfile.txt
028fc9f1c34dc30358d650ab61c757f1e087545690642e24ede8d947a146af4c yourfile.txt使用默认算法 sha224来计算文件sha
➜ ~ shasum yourfile.txt
1b2ed9e3929e0461108cf2c224485ba75135844b yourfile.txt
命令选项：
-a, --algorithm 1 (default), 224, 256, 384, 512, 512224, 512256
-b, --binary read in binary mode
-c, --check read SHA sums from the FILEs and check them
--tag create a BSD-style checksum
-t, --text read in text mode (default)
-U, --UNIVERSAL read in Universal Newlines mode
produces same digest on Windows/Unix/Mac
-0, --01 read in BITS mode
ASCII '0' interpreted as 0-bit,
ASCII '1' interpreted as 1-bit,
all other characters ignored
The following five options are useful only when verifying checksums:
--ignore-missing don't fail or report status for missing files
-q, --quiet don't print OK for each successfully verified file
-s, --status don't output anything, status code shows success
--strict exit non-zero for improperly formatted checksum lines
-w, --warn warn about improperly formatted checksum lines
-h, --help display this help and exit
-v, --version output version information and exit
When verifying SHA-512/224 or SHA-512/256 checksums, indicate the
algorithm explicitly using the -a option, e.g.
shasum -a 512224 -c checksumfile
The sums are computed as described in FIPS PUB 180-4. 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, `U' for UNIVERSAL, `^' for BITS),
and name for each FILE. The line starts with a `\' character if the
FILE name contains either newlines or backslashes, which are then
replaced by the two-character sequences `\n' and `\\' respectively.
