mac命令行下计算文件SHA-256散列值

源起

从国内的第三方网站下载了Android sutiod的zip包下载地址，为了安全起见还是得跟Android官网上的对应的zip包的SHA值做下对比。以前是经常使用md5命令的，所以理论在命令行下应该是有对应的命令行工具可以计算SHA值的。后来搜索到可以用 shasum命令来完成我的需求。

我们man一下shasum命令，注：需要注意-a参数，即计算文件散列值时可以选择具体的算法

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SHASUM(1)                                                     Perl Programmers Reference Guide                                                     SHASUM(1)


NAME
       shasum - Print or Check SHA Checksums

SYNOPSIS
        Usage: shasum [OPTION]... [FILE]...
        Print or check SHA checksums.
        With no FILE, or when FILE is -, read standard input.

          -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.

实践

PS: sha256算法的散列值是256个byte，即256/8=32字节，1个字节用2位16制表示，即散列值的长度为64个字符

对比一下官网的信息，good，安全较验通过！

回顾

md5与sha256的区别

计算字符串长度

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${#字符串变量}