uniq [OPTIONS] INPUT OUTPUT

-c, --count
    prefix lines by the number of occurrences

-d, --repeated
    only print duplicate lines, one for each group

-D     print all duplicate lines

--all-repeated[=METHOD]
    like -D, but allow separating groups with an empty line;
    METHOD={none(default),prepend,separate}

-f, --skip-fields=N
    avoid comparing the first N fields

--group[=METHOD]
    show all items, separating groups with an empty line;
    METHOD={separate(default),prepend,append,both}

-i, --ignore-case
    ignore differences in case when comparing

-s, --skip-chars=N
    avoid comparing the first N characters

-u, --unique
    only print unique lines

-z, --zero-terminated
    line delimiter is NUL, not newline

-w, --check-chars=N
    compare no more than N characters in lines

--help
    display this help and exit

--version
    output version information and exit

uniq file1

uniq -c file1

uniq -D file1

uniq -u file1

uniq -s 4 file1

uniq -w 3 file1

uniq -i file1

uniq -z file1