如何在bash中的多字符定界符上拆分字符串? [英] Howto split a string on a multi-character delimiter in bash?
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问题描述
为什么下面的bash代码不起作用?
Why doesn't work the following bash code?
for i in $( echo "emmbbmmaaddsb" | split -t "mm" )
do
echo "$i"
done
预期输出:
e
bb
aaddsb
推荐答案
由于需要换行符,因此只需用换行符替换字符串中所有mm
实例.在纯本地bash中:
Since you're expecting newlines, you can simply replace all instances of mm
in your string with a newline. In pure native bash:
in='emmbbmmaaddsb'
sep='mm'
printf '%s\n' "${in//$sep/$'\n'}"
如果要在更长的输入流上进行此类替换,则最好使用awk
,因为bash的内置字符串操作不能很好地扩展到超过几千字节的内容. BashFAQ#21 中给出的gsub_literal
shell函数(后端到awk
)适用:
If you wanted to do such a replacement on a longer input stream, you might be better off using awk
, as bash's built-in string manipulation doesn't scale well to more than a few kilobytes of content. The gsub_literal
shell function (backending into awk
) given in BashFAQ #21 is applicable:
# 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;
}
'
}
...在这种情况下,用作:
...used, in this context, as:
gsub_literal "mm" $'\n' <your-input-file.txt >your-output-file.txt
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