how to replace a character with blank in a file

Shell Programming and Scripting
1

hi,

I have a doubt in replacing characters with blank.

My requirement is that, i have one file and looks like below

4:ALTER SYSTEM DISCONNECT SESSION '193,191' IMMEDIATE;
6:ALTER SYSTEM DISCONNECT SESSION '205,7274' IMMEDIATE;
5:ALTER SYSTEM DISCONNECT SESSION '206,34158' IMMEDIATE;
8:ALTER SYSTEM DISCONNECT SESSION '211,154' IMMEDIATE;

i want remove first two characters in every line (i mean 4: like that), i have tried through sed like below

sed s/[1-4]://g

but not working

Thanks,
Sri.

2 
sed 's/..//' file
3

Below code is not working (it not modifying with blank space).

4

Sorry, misread that:

sed 's/../ /' file

The output goes to stdout, to change the file you can use the -i option if your sed version supports that otherwise you can use a temporary file:

sed 's/../ /' file > tempfile && mv tempfile file
5

try this

 
sed 's/^[0-9]:/  /g'  infile