How to read and replace Special characters in a fixed length file using shell script - shell

Question

I have a fixed length file in which some records have different special characters like Еӏєпа
I'm able to select those records containing special characters/.
I want to read 2 columns from those records and update it with '*' padded with blanks
Sample Data :
1234562013-09-01 01:05:30Еӏєпа Нцвѡі A other
5657812011-05-05 02:34:56abu jaya B other
Specifically, the 3rd and 4th column containing special characters, should be replaced with a single '*' padded with blanks to fill the length
I need result like below
1234562013-09-01 01:05:30* * A2013-09-01 02:03:40other
5657812011-05-05 02:34:56abu jaya B2013-09-01 07:06:10other
Tried the following commands :
sed -r "s/^(.{56}).{510}/\1$PAD/g;s/^(.{511}).{1023}/\1$PAD/g" errorline.txt
cut -c 57-568
Could someone help me out with this?

Answer 1

I would go with awk, something like:
awk '/[LIST__OF_SPECIAL_CHARS]/ {
l=$0
# for 3rd col
# NOTE the * must be padded if you have a fixed length file
# This can be done with spaces and/or (s)printf, read the docs
if (substr($0,FROM,NUM_OF_CHARS) ~ /[LIST__OF_SPECIAL_CHARS]/) {
l=substr(l,1,START_OF_3RD_COL_MINUS_1) "*" substr(l,START_OF_4TH_COL)
}
# for 4th col
# NOTE the * must be padded if you have a fixed length file
# This can be done with spaces and/or (s)printf, read the docs
if (substr($0,START_OF_4TH_COL,NUM_OF_CHARS) ~ /[LIST__OF_SPECIAL_CHARS]/) {
l=substr(l,1,START_OF_4TH_COL_MINUS_1) "*" substr(l,END_OF_4TH_COL_PLUS_1)
}
# after printing this line, skip to next record.
print l
next
}
{ # prints every other record
print }' INPUTFILE

Answer 2

sed "/.\{56\}.*[^a-zA-Z0-9 ].*.\{7\}/ s/\(.\{56\}\).\{20\}\(.\{7\}\)/\1* * \2/"errorline.txt
where:
56 is the first part of your line that don't contain special char
20 is the second part taht contain maybe special char
7 is the last part, end of your string.
"* * " is the string that will replace your special char section.
Adapt those values to your string structure
This sed read all the file and replace only the lines with special char.