如何在bash中拆分多字符分隔符上的字符串？

Question

为什么下面的bash代码不起作用？

for i in $( echo "emmbbmmaaddsb" | split -t "mm"  )
do
    echo "$i"
done

预期产出：

e
bb
aaddsb

Answer 1

由于您需要换行符，您可以简单地用换行符替换字符串中mm的所有实例。在纯正的本地bash中：

in='emmbbmmaaddsb'
sep='mm'
printf '%s\n' "${in//$sep/$'\n'}"

如果您希望对较长的输入流进行这样的替换，那么最好使用awk，因为bash的内置字符串操作不能很好地扩展到几KB以上的内容。BashFAQ#21中给出的gsub_literalshell函数（后端到awk)适用：

# Taken from http://mywiki.wooledge.org/BashFAQ/021

# usage: gsub_literal STR REP
# replaces all instances of STR with REP. reads from stdin and writes to stdout.
gsub_literal() {
  # STR cannot be empty
  [[ $1 ]] || return

  # string manip needed to escape '\'s, so awk doesn't expand '\n' and such
  awk -v str="${1//\\/\\\\}" -v rep="${2//\\/\\\\}" '
    # get the length of the search string
    BEGIN {
      len = length(str);
    }

    {
      # empty the output string
      out = "";

      # continue looping while the search string is in the line
      while (i = index($0, str)) {
        # append everything up to the search string, and the replacement string
        out = out substr($0, 1, i-1) rep;

        # remove everything up to and including the first instance of the
        # search string from the line
        $0 = substr($0, i + len);
      }

      # append whatever is left
      out = out $0;

      print out;
    }
  '
}

...在本上下文中用作：

gsub_literal "mm" $'\n' <your-input-file.txt >your-output-file.txt