we must firstly use the sort command, because of uniq command process for sequential lines.therefore we use firstly sort command for get the sequential lines.

Code:

# cat file
a b
b c
a b
d c
a b
a b

uniq + sort (unsuccesfull)

Code:

# cut -f1 -d' ' file|uniq -c
      1 a
      1 b
      1 a
      1 d
      2 a

Code:

# cut -f1 -d' ' file|uniq -c|sort
      1 a
      1 a
      1 b
      1 d
      2 a

sort + uniq (successfull)

Code:

# cut -f1 -d' ' file|sort
a
a
a
a
b
d

Code:

# cut -f1 -d' ' file|sort|uniq -c
      4 a
      1 b
      1 d

and with sed

Code:

# sed 's/ *\(.*\) \(.*\)/\2  \1/'

s (substitute) --> s/regexp/replacement/
* --> represent the initial "spaces" of string (between the quotes)

Code:

"      "4 a
"      "1 b
"      "1 d

\(.*\) --> 4 --> \(.*\) this strucutes saves the our string (.* is means everything) --> represent '\1' while writes it
and there is a space " "
\(.*\) --> a --> represent '\2' while writes it

finaly we write our values to stdoutp
\2 --> a
and two spaces
\1 --> 4

Code:

# cut -f1 -d' ' file |sort|uniq -c|sed 's/ *\(.*\) \(.*\)/\2 \1/'
a  4
b  1
d  1

regards
ygemici