Bash 在文本字符串中替换变量
bash中的变量中有一个文本字符串,如下所示:Bash 在文本字符串中替换变量,bash,shell,macros,variable-substitution,Bash,Shell,Macros,Variable Substitution,bash中的变量中有一个文本字符串,如下所示: filename1.txt filename2.txt varname1 = v1value $(varname1)/filename3.txt $(varname1)/filename4.txt varname2 = $(varname1)/v2value $(varname2)/filename5.txt $(varname2)/filename6.txt 我想替换所有的变量,产生以下结果: filename1.txt filename2
filename1.txt
filename2.txt
varname1 = v1value
$(varname1)/filename3.txt
$(varname1)/filename4.txt
varname2 = $(varname1)/v2value
$(varname2)/filename5.txt
$(varname2)/filename6.txt
我想替换所有的变量,产生以下结果:
filename1.txt
filename2.txt
v1value/filename3.txt
v1value/filename4.txt
v1value/v2value/filename5.txt
v1value/v2value/filename6.txt
有人能提出一个干净的方法在shell中实现这一点吗?我使用
m4
找到了一个合理的解决方案:
function make_substitutions() {
# first all $(varname)s are replaced with ____varname____
# then each assignment statement is replaced with an m4 define macro
# finally this text is then passed through m4
echo "$1" |\
sed 's/\$(\([[:alnum:]][[:alnum:]]*\))/____\1____/' | \
sed 's/ *\([[:alnum:]][[:alnum:]]*\) *= *\(..*\)/define(____\1____, \2)/' | \
m4
}
或许
echo "$string" | perl -nlE 'm/(\w+)\s*=\s*(.*)(?{$h{$1}=$2})/&&next;while(m/\$\((\w+)\)/){$x=$1;s/\$\($x\)/$h{$x}/e};say$_'
印刷品
filename1.txt
filename2.txt
v1value/filename3.txt
v1value/filename4.txt
v1value/v2value/filename5.txt
v1value/v2value/filename6.txt
在awk中:
BEGIN {
FS = "[[:space:]]*=[[:space:]]*"
}
NF > 1 {
map[$1] = $2
next;
}
function replace( count)
{
for (key in map) {
count += gsub("\\$\\("key"\\)", map[key])
}
return count
}
{
while (replace() > 0) {}
print
}
在卢阿:
local map = {}
--for line in io.lines("file.in") do -- To read from a file.
for line in io.stdin:lines() do -- To read from standard input.
local key, value = line:match("^(%w*)%s*=%s*(.*)$")
if key then
map[key] = value
else
local count
while count ~= 0 do
line, count = line:gsub("%$%(([^)]*)%)", map)
end
print(line)
end
end
这个文件有多大?这类问题实际上可以通过一个好的文本编辑器手动更快地解决,除非文件真的很大。这只是一个示例。实际上有几百个这样的文件,每个文件中有0到20个替换。您可以将这种模式用于任何允许这种运行时计算的语言或模板/宏系统。您甚至可以通过一些努力(和消毒)来使用shell本身。一个(可能是单程)awk解决方案也应该相当简单。