wc [OPTION]... [FILE]...

-c, --bytes            print the byte counts
-m, --chars            print the character counts
-l, --lines            print the newline counts
    --files0-from=F    read input from the files specified by
                         NUL-terminated names in file F;
                         If F is - then read names from standard input
-L, --max-line-length  print the maximum display width
-w, --words            print the word counts
    --help     display this help and exit
    --version  output version information and exit

wc -l file.txt