md5sum 的使用

1. 基本命令

$ md5sum --help
Usage: md5sum [OPTION]... [FILE]...
Print or check MD5 (128-bit) checksums.
With no FILE, or when FILE is -, read standard input.

  -t, --text           read in text mode (default)
  -b, --binary         read in binary mode
  -c, --check          read MD5 sums from the FILEs and check them
      --tag            create a BSD-style checksum
  Note: There is no difference between binary and text mode option on GNU system.

The following four 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
      --strict         exit non-zero for improperly formatted checksum lines
  -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 input mode ('*' for binary,
space for text), and name for each FILE.

2. 验证文件是否被篡改

把下载的文件file和该文件的file.md5报文摘要文件放在同一个目录下，然后用如下命令进行验证：

md5sum -c file.md5

md5sum命令还可以一次验证多个文件。如果将所需验证的文件名写入一个单独的文件，则可以使用该文件检查是否有任何文件已更改。

$ md5sum file1.txt file2.txt file3.txt > hashes
$ md5sum --check hashes
file1.txt: OK
file2.txt: OK
file3.txt: OK

3. 批量查看md5值

md5sum filename > filename.md5 # 创建单独的md5文件
md5sum *.filename > filename.md5 # 将所有文件的md5输入到一个文件中

# 让每个文件单独生成一个md5文件
for n in `ls *.fastq.gz`; do md5sum $n > ${n%.fastq.gz}.md5; done

# 创建sh文件用于批量运行
for n in `ls *.fastq.gz`; do echo "md5sum $n > ${n%.fastq.gz}.md5">>createmd5.sh; done

for n in `ls * R?.fq.gz`; do echo "md5sum $n > ${n%.fq.gz}.md5">>createmd5.sh; done