how to restrict length of string present in a line using linux

In bash, you can use the following to limit the string, in this case, from index 0 to index 17.

$ var="this is a another string"

$ echo ${var:0:17}

this is a another

Using awk, by columns :

$ awk '{print $1, $2, $3, $4}' file

or with sed :

sed -r 's@^(\S+\s+\S+\s+\S+\s+\S+).*@\1@' file

or by length using cut :

$ cut -c 1-23 file

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