[SOLVED] stop sed from replacing unicode hex characters

bradvan · 11-19-2019, 07:27 AM

I have a variable with some unicode hex characters:

Code:

LABEL=$(blkid CentOS-7-x86_64-DVD-1810.iso | awk '{ print $2, $3, $4 }' | sed -e 's| | \\x20|g' | sed -e 's|"||g")

which results in:

Code:

echo ${LABEL}
LABEL=CentOS\x207.6\x20x86_64

Now, I want to insert that in a file:

Code:

sed -e "/^label linux/ i label kickstart\n  menu label ^Kickstart CentOS 7\n  kernel vmlinux\n  append initrd=initrd.img inst.stage2=hd:${LABEL} inst.ks=cdrom:/ks.cfg\n" isolinux.cfg

which changes the unicode hex

Code:

\x20

back to a space. Any ideas on how to keep that from happening?

pan64 · 11-19-2019, 08:57 AM

probably you need to use double \ instead of single ones in LABEL.

teckk · 11-19-2019, 09:00 AM

I don't really understand your sed line

Couple of examples:

Code:

LABEL=CentOS\x207.6\x20x86_64
echo "$LABEL"
CentOSx207.6x20x86_64

LABEL="CentOS\x207.6\x20x86_64"
echo "$LABEL"
CentOS\x207.6\x20x86_64

An to echo that to file:

Code:

echo "$LABEL" > test.txt
cat test.txt
CentOS\x207.6\x20x86_64

bradvan · 11-19-2019, 11:25 AM

The first command gives the the variable in the required format. However, when I go to insert it into isolinux.cfg, at that point sed replaces the unicode hex string with an ascii space. I guess I just shouldn't bother with changing to unicode hex when I create the variable. Go ahead an insert it with sed, then issue a second sed command to change those two spaces to the unicode hex. That seems like the most expedient way to do it.

michaelk · 11-19-2019, 12:34 PM

I think you need to define what unicode character set you are using. I don't think its sed's fault.

The echo command displays as posted because escape characters are not interpreted by default. The -e option enables escape characters and therefore compare the outputs:

echo ${LABEL}
versus
echo -e ${LABEL}

Since I am a native English speaker I have not paid enough attention character sets. It depends on what unicode character set you are using, what application you are using to view the file and how it interprets the characters. Many unicodes sets are backwards compatible with ASCII and therefore \x20 is a space.

As I had time to think a bit more I would refrain from using spaces the disk label. Maybe underscore or a hyphen.

Firerat · 11-19-2019, 02:45 PM

why all the messing about to get a space?

Code:

LABEL=CentOS$'\x20'7.6$'\x20'x86_64
cat -A - <<<$LABEL 

LABEL="CentOS 7.6 x86_64"
cat -A - <<<$LABEL 


#

an no need for the sed, awk can do sub() and gsub()

michaelk · 11-19-2019, 04:25 PM

Quote:

By default, the inst.stage2= boot option is used on the installation media and set to a specific label (for example, inst.stage2=hd:LABEL=RHEL7\x20Server.x86_64).

I had to go back to the documentation... Hmm, it does show a space... I agree with pan64 that a double \\ should work.

Firerat · 11-19-2019, 04:54 PM

https://wiki.syslinux.org/wiki/index...e=Config#LABEL

or not

https://wiki.syslinux.org/wiki/index...=Config#APPEND
https://wiki.syslinux.org/wiki/index...=Config#INITRD

as for getting the Label

instead of messing about with awk/sed

Code:

MyISO="/path/to/CentOS-7-x86_64-DVD-1810.iso"
LABEL="$( /sbin/blkid -s LABEL -o value "${MyISO}" )"
echo ${LABEL// /_}


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bradvan · 11-20-2019, 04:42 AM

Thanks everyone! I'm trying to have a script to edit an isolinux.cfg file while creating a custom kickstart ISO image. I have it working with:

Code:

LABEL=$(blkid CentOS-7-x86_64-DVD-1810.iso | awk '{ print $2, $3, $4 }' | sed -e 's|"||g")
sed -i "/^label linux/ i label kickstart\n  menu label ^Kickstart CentOS 7\n  kernel vmlinux\n  append initrd=initrd.img inst.stage2=hd:${LABEL} inst.ks=cdrom:/ks.cfg\n" isolinux.cfg
read -r -a LBL <<< ${LABEL}
sed -i "s|\(${LBL[0]}\) \($LBL[1]}\) \(${LBL[2]}\)|\1\\\x20\2\\\x20\3|" isolinux.cfg

Thanks again for the help!

Firerat · 11-20-2019, 05:42 AM

my spin on it

Code:

#!/bin/bash
Entry () {
cat <<EOF
label kickstart\n\
  menu label ^Kickstart ${LABEL% *}\n\
  kernel vmlinux\n\
  append initrd=initrd.img\
 inst.stage2=hd:UUID=${UUID} LABEL=${LABEL// /\\\\\x20}\
 inst.ks=cdrom:\/ks.cfg
EOF
}
MyISO="/path/to/CentOS-7-x86_64-DVD-1810.iso"
eval $( /sbin/blkid -s UUID -s LABEL -o export "${MyISO}" )

sed "/^label linux/ i $(Entry)" isolinux.cfg


#

[edit]
and, to start to making it more robust

Code:

MyISO="${1-/path/to/default.iso}"

#
# ...
#
if [[ ${LABEL} ]]
then
  sed "/^label linux/ i $(Entry)" isolinux.cfg
else
  echo "failed to probe ${MyISO}"
fi


#