Подсчёт количества символов, слов и строк [в файле]

Для всего вышеуказанного служит команда wc.
man wc:

NAME
   wc -- word, line, character, and byte count

SYNOPSIS
   wc [-Lclmw] [file ...]

...
The following options are available:

   -L      The number of characters in the longest input line is written to
           the standard output.  When more then one file argument is speci-
           fied, the longest input line of all files is reported as the
           value of the final ``total''.

   -c      The number of bytes in each input file is written to the standard
           output.  This will cancel out any prior usage of the -m option.

   -l      The number of lines in each input file is written to the standard
           output.

   -m      The number of characters in each input file is written to the
           standard output.  If the current locale does not support multi-
           byte characters, this is equivalent to the -c option.  This will
           cancel out any prior usage of the -c option.

   -w      The number of words in each input file is written to the standard
           output.
...
ENVIRONMENT
   The LANG, LC_ALL and LC_CTYPE environment variables affect the execution
   of wc as described in environ(7).

EXIT STATUS
   The wc utility exits 0 on success, and >0 if an error occurs.

EXAMPLES
   Count the number of characters, words and lines in each of the files
   report1 and report2 as well as the totals for both:

         wc -mlw report1 report2

   Find the longest line in a list of files:

         wc -L file1 file2 file3 | fgrep total
HISTORY
   A wc command appeared in Version 1 AT&T UNIX.