How can I make the list of letters from A to Z and iterate through them in the shell?

Question

Say I want to iterate from letter A to letter Z in csh shell. How do I succinctly do that?

In bash I would do something like

for i in 'A B C ...Z'; do echo $i; done

The point is I don't want to write A through Z, I want something like

[A-Z]

Can you suggest a one line suggestion in AWK or Perl?

Answer 1

perl -e 'print for "a" .. "z", "A" .. "Z", 0 .. 9'

Answer 2

Perl

$,=" ";print +(A..Z)

or to use inside a shell:

for i in `perl -e '$,=" ";print +(A..Z)'` ; do echo $i ; done

Answer 3

Hope you have Ruby installed. ;) See this, plain command-line from the shell:

1. using Ruby to iterate from A to Z and ask to print the letters:

   $ ruby -e ' "a".upto("z") {|letter| print letter}; print "\n"'
   

2. iterate from A to Z and substitute the value obtained during the current iteration into a string, then print the string:

   $ ruby -e ' "a".upto("z") {|letter| puts "mkdir #{letter}"}'
   

   mkdir a
   mkdir b
   mkdir c
   mkdir d
   ...
   mkdir z
   

3. use the output of the iteration from A to C as an argument to mkdir, in order to create 3 directories:

   $ mkdir $(ruby -e ' "a".upto("c") {|letter| puts "#{letter}"}')
   

   do a listing to see the results:

   $ ls -al
   drwxr-xr-x  2 iuliu users  4096 2009-10-07 00:09 a
   drwxr-xr-x  2 iuliu users  4096 2009-10-07 00:09 b
   drwxr-xr-x  2 iuliu users  4096 2009-10-07 00:09 c
   

Hope this helps a bit! ;)

regards, Iuliu

Answer 4

nobody has gawk solution, therefore here's one

awk 'BEGIN{for(i=65;i<=90;i++) printf "%c", i}'

Answer 5

How about:

for i in $(perl -e 'for my $i ("a".."z") { print "$i "; }'); do ...; done

... or am I misunderstanding what you're trying to accomplish?

(Admittedly the suggestion using $,=" " is even better than the explicit Perl for loop). However, I don't understand value of wrapping the range in +() punctuation. It works for me if I just use: print A..Z; ... though perl -we 'print a..z;' gives me a warning about unquoted strings, but the uppercase version doesn't. The statementprint +(a..z)gives exactly the same warning ... and quoting any of these eliminates the warning. So what's the intent of the+(...)`? Is it just trying to force this into a list context?)

Answer 6

foreach i (`jot -c 26 65`)
    echo $i
end

Answer 7

USING AWK:

You can refer to the ASCII Character Set using the following link:

http://ee.hawaii.edu/~tep/EE160/Book/chap4/subsection2.1.1.1.html

Now to iterate through any set of value, you can use the AWK command as follows:

awk 'BEGIN{ for(i=97;i<123;i++){printf "%c ",i}; printf "\n";}'

Result: a b c d e f g h i j k l m n o p q r s t u v w x y z

Here 97 corresponds to letter "a" and 122 is "z". You can vary the result by using any of the value from the list given above.

• 65 to 90 for A to Z
• 48 to 57 for 0 to 9
• 97 to 122 for a to z

and so on.

Answer 8

I had exactly the same question. The obvious Windows use case is iterating through a list of drive letters. This works in Cygwin:

for i in a b {d..z}; do (du -s "/cygdrive/$i;"); done

Or another example:

for i in a b {d..h} {r..u}; do df /cygdrive/$i | grep -v Filesystem; done

Or yet another example using Perl - thanks to Jim Dennis for his inspiration:

perl -e 'for my $i ("a","b","d".."i","r".."v") { print "$i\n"; }' | sed -e 's/^/\/cygdrive\//'