Perl/Sed command to replace same pattern multiple times

Question

I need to set disable=no in /etc/xinetd.d/chargen using commands like perl or sed.

/etc/xinetd.d/chargen content is:

# description: An xinetd internal service which generate characters.  The
# xinetd internal service which continuously generates characters until the
# connection is dropped.  The characters look something like this:
# !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefg
# This is the tcp version. 
service chargen
{
        disable         = yes
        type            = INTERNAL
        id              = chargen-stream
        socket_type     = stream
        protocol        = tcp
        user            = root
        wait            = no 
}

# This is the udp version. 
service chargen
{
        disable         = yes
        type            = INTERNAL
        id              = chargen-dgram
        socket_type     = dgram
        protocol        = udp
        user            = root
        wait            = yes 
}

I have used perl command

perl -0777 -pe 's|(service chargen[^\^]+)disable\s+=\syes|\1disable=no|' /etc/xinetd.d/chargen 

but it is replacing at only one place.

# description: An xinetd internal service which generate characters.  The
# xinetd internal service which continuously generates characters until the
# connection is dropped.  The characters look something like this:
# !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefg
# This is the tcp version.
service chargen
{
        disable         = yes
        type            = INTERNAL
        id              = chargen-stream
        socket_type     = stream
        protocol        = tcp
        user            = root
        wait            = no
}

# This is the udp version.
service chargen
{
        disable=no
        type            = INTERNAL
        id              = chargen-dgram
        socket_type     = dgram
        protocol        = udp
        user            = root
        wait            = yes
}

what is the proper command to make it work in both places?

NOTE: I could have replaced disable = yes with disable = no without matching service chargen but I need to use same sed/perl command to replace in /etc/xinetd.conf which will have other services too.

UPDATE As Jonathan highlighted in his comment, disable can be at any position inside the flower bracket.

Answer 1

Using sed, you can use:

sed -e '/^service chargen/,/^}/ { /disable *= yes/ s/yes/no/; }'

The first part searches for ranges of lines from one starting service chargen to the first line afterwards that starts with }; within that range, it looks for lines containing disable = yes with arbitrary numbers of spaces between disable and the = yes, and changes the yes to no. If necessary, you can make the regexes fussier (no trailing white space; don't edit service chargen2018 blocks, demand the } have no trailing blanks, etc.) but it probably isn't necessary.

You can often do in-place editing, but beware of differences between systems in the semantics of how you do that. (BSD and macOS require -i ''; GNU only requires -i; both accept -i.bak and it means the same in both — but you have a backup file to cleanup.)