Trying to use sed - but having no luck.
I have a text file - I want to replace whatever character is in position 106, 157 and 237 w/ the string "xxx". Want this change for all lines w/in that text file.
I'm open to using awk or whatever command would be best for replacing characters based on the exact position. Seems like sed can do a lot, but for whatever reason, have had no luck figuring out how to replace on just position alone.
Thanks much!
I know its Perl, and it looks ugly, but if you don't mind that then here it goes:
perl -pe 's/(.{105}).(.{50}).(.{79}).(.*)/\1xxx\2xxx\3xxx\4/' file > out.file
I hope I didn't mess numbering 
works great. thanks again!
sed -n 's/\(.\{105\}\).\(.\{50\}\).\(.\{79\}\).\(.*\)/\1XXX\2XXX\3X\4/gp' sample_file
sed 's/./xxx/237;s/./xxx/157;s/./xxx/106' infile
awk -F "" '{for (i=1;i<=NF;i++) if (i==106||i==157||i==237) $i="xxx"}1' OFS="" urfile