List the content of a directory specified by loop indices
<p>I'm working with numerical weather forecast  named as follow:</p>

<pre><code>sub_gfsanl_4_2011MMDD-IIII-FFFF.grb2
</code></pre>

<p>-MM stands for month  from 01 to 12 </p>

<p>-DD stands for days   from 01 to 31</p>

<p>-IIII stands for initialisation time, the first and second digits are for hours the third and last are for minutes</p>

<p>-FFFF stands for forecast hour , the first and second digits are for hours the third and last are for minutes</p>

<p>In my directory I have several files for a given days of a given months. A day has 4 data, one at every six hours IIII=0000 ,0600,1200,1800.</p>

<p>What I'm trying to do is to list all files of a given days, here the f90 code I wrote:</p>

<pre><code>program test_ec

implicit none

!==variable declaration==

integer :: mi,di,dil,mil
character*3 :: temp

!==Program instructions==

mil=1
write(temp,'(i2.2)') mil
read(temp,'(i2.2)') mi
!convert the month into a two digit value mi=01  


 ! change to directory where the data are stored
 CALL chdir('/media/Hello/ncfiles/GFS' )

do dil=1,31

     !loop over days
     write(temp,'(i2.2)') dil
     read(temp,'(i2.2)') di

     ! converting day number into a two digit number, store this value into di. ex dil=9 then di=09

CALL execute_command_line( 'ls sub_gfsanl_4_2011${mi}${di}*.nc &gt; yes.txt' )
!list all files with the correct month and days and store it to yes.txt

end do

end program test_ec
</code></pre>

<p>For some reasons the <code>execute_command_line</code> doesn't seem to like the $ for variable...</p>