Как настроить локальный прокси для перенаправления трафика на удаленные прокси?

Я только что написал и протестировал в MacOS High Sierra:

#!/bin/sh

for fl in *.xml
do
    filename=$(echo $fl | cut -f 1 -d '.' | sed 's/_DANY$//')

    sed -i.orig '1a\
    <media:content url="'$filename'.mpg" type="video/mpg" expression="full" /> \
    ' $fl
done

ls *.xml     search in current directory
-i.orig     backup of original files with suffix
'1a..'      insert into second line

BSD sedв MacOS имеют несколько отличий от GNU sed, поэтому следующее выражение нужно писать отдельными строками:

'1a \        # backslash and newline
 some text'  

Символ новой строки \nне распознается, поэтому следует писать:

'1a \
some text   # newline here
'

вместо:

'1a \
some text\n'

Использование:

yurijs-MacBook-Pro:sed yurij$ cat *.xml
<description>Entrepreneur James overcame unconscionable childhood abuse before the sins of his past came back to haunt him.</description>
<media:rating>TV-14</media:rating>
<description>Entrepreneur James overcame unconscionable childhood abuse before the sins of his past came back to haunt him.</description>
<media:rating>TV-14</media:rating>
yurijs-MacBook-Pro:sed yurij$./cli
yurijs-MacBook-Pro:sed yurij$ cat *.xml
<description>Entrepreneur James overcame unconscionable childhood abuse before the sins of his past came back to haunt him.</description>
<media:content url="24ToLife_AFamilyDivided_191045.mpg" type="video/mpg" expression="full" />
<media:rating>TV-14</media:rating>
<description>Entrepreneur James overcame unconscionable childhood abuse before the sins of his past came back to haunt him.</description>
<media:content url="tt.mpg" type="video/mpg" expression="full" />
<media:rating>TV-14</media:rating>