Assume each line has 51 fields, the delimiter is “,”, and we want to remove fields 31 to 50,

cut -d, -f1-30,51- input_file > output_file

Some other file operations:
1. Get the last N lines from a file:

tail -n N INPUT_FILE > OUTPUT_FILE

2. Cat two files together

cat FILE1 FILE2 >> FILE3

3. Combine the columns from two files:

paste -d , FILE1 FILE2 > FILE3