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arctica
Joined: 10 Sep 2006
Posts: 148
Location: United Kingdom
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 Posted: Wed Jan 29, 2025 4:46 pm Post subject: Running command line programs |
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Hello,
I have tested the following code (ftn95 v9.06), which works using system but fails with execute_command_line:
| Code: |
program dos_cmd
integer :: i
character(len=512) :: cmd
!Input string using programs grdinfo, piping and gawk (programs in PATH)
!Get header info from a netCDF file using GMT
cmd = 'grdinfo Bathy_crop1_scaled.grd -C | ' // &
'gawk "{xmin=$2; xmax=$3; ymin=$4; ymax=$5; nx=$10; ny=$11};' // &
'{print xmin, xmax, ymin, ymax, 2*nx, 2*ny}" > nxy.txt'
print *, "Executing command:"
print *, trim(cmd)
!test alternate command-line calls
call system(cmd) ! works
call execute_command_line(cmd, exitstat=i) ! fails (F2008 intrinsic)
print *, "Exit status of external_prog.exe was ", i
end program dos_cmd
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system(cmd) correctly writes nxy.txt. However execute_command_line(cmd,exitstat=i) fails with run-time error:
| Code: |
Executing command:
grdinfo Bathy_crop1_scaled.grd -C | gawk "{xmin=$2; xmax=$3; ymin=$4; ymax=$5; nx=$10; ny=$11};{print xmin, xmax, ymin,
ymax, 2*nx, 2*ny}" > nxy.txt
grdinfo [ERROR]: Cannot find file |
grdinfo [ERROR]: Cannot find file gawk
grdinfo [ERROR]: Cannot find file {xmin
Exit status of external_prog.exe was 72 |
Any ideas why the second call fails? grdinfo, gawk all sit in the windows PATH.
Not a big issue, just curious to know why there is a difference in behaviour.
Lester |
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Kenneth_Smith
Joined: 18 May 2012
Posts: 868
Location: Lanarkshire, Scotland.
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| Posted: Wed Jan 29, 2025 8:20 pm Post subject: |
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| What do the optional arguments CMDSTAT, and CMDMSG return? |
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arctica
Joined: 10 Sep 2006
Posts: 148
Location: United Kingdom
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| Posted: Thu Jan 30, 2025 2:02 am Post subject: |
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Hi Ken,
Adding the cmdstat and cmdmsg options gives:
| Code: |
Executing command:
grdinfo Bathy_crop1_scaled.grd -C | gawk "{xmin=$2; xmax=$3; ymin=$4; ymax=$5; nx=$10; ny=$11};{print xmin, xmax, ymin,
ymax, 2*nx, 2*ny}" > nxy.txt
grdinfo [ERROR]: Cannot find file |
grdinfo [ERROR]: Cannot find file gawk
grdinfo [ERROR]: Cannot find file {xmin
Exit status of external_prog.exe was 72
cmdstat = 0
cmdmsg =�
�@��@h� `� p� ��@
� � 8� 8�
�
�PCNAME
PCNAME
@ |
The extra options, i, j (integers) and csmg (character)
| Code: |
| call execute_command_line(cmd, exitstat=i, cmdstat=j, cmdmsg=csmg) ! fails (F2008 intrinsic) |
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wahorger
Joined: 13 Oct 2014
Posts: 1278
Location: Morrison, CO, USA
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| Posted: Thu Jan 30, 2025 2:13 am Post subject: |
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A general problem might be the use of the pipe.
Windows does not operate like Linux, specifically that a pipe does not concurrently run at the same time as the "sending" command.
Or, so I have been told/read. |
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PaulLaidler
Site Admin
Joined: 21 Feb 2005
Posts: 8316
Location: Salford, UK
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| Posted: Thu Jan 30, 2025 10:07 am Post subject: |
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EXECUTE_COMMAND_LINE has an optional logical argument WAIT which when present and set .FALSE. executes the command asynchronously.
But I think that SYSTEM is the same as EXECUTE_COMMAND_LINE with WAIT set .TRUE. which is the default. |
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arctica
Joined: 10 Sep 2006
Posts: 148
Location: United Kingdom
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| Posted: Thu Jan 30, 2025 1:12 pm Post subject: |
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The solution when using execute_command_line(cmd) is to wrap the command in a shell invoccation, as that was the only way to get it to understand piping and redirection.
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cmd2 = 'cmd.exe /c "grdinfo Bathy_crop1_scaled.grd -C | ' // &
'gawk "{xmin=$2; xmax=$3; ymin=$4; ymax=$5; nx=$10; ny=$11};' // &
'{print xmin, xmax, ymin, ymax, 2*nx, 2*ny}" > nxy_test.txt" ' |
The output of exitstat and cmdstat are 0 (process succeds), however the output from cmdmsg is garbage
As you say Paul, SYSTEM and EXECUTE_COMMAND_LINE do the same thing.
Lester |
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Kenneth_Smith
Joined: 18 May 2012
Posts: 868
Location: Lanarkshire, Scotland.
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| Posted: Thu Jan 30, 2025 2:45 pm Post subject: |
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Lester,
cmdmsg has intent(inout) so needs to be initialised to " ".
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program p
implicit none
integer :: cstat, estat
character(100) :: cmsg
cmsg = ' '
! This will fail since xxx.exe does not exist
call execute_command_line ("xxx.exe", wait=.true., exitstat=estat, cmdstat=cstat, cmdmsg=cmsg)
if (cstat .gt. 0) print *, "Command execution failed with error " , trim( cmsg )
end |
Returns
| Code: |
| Command execution failed with error Failed to create process. |
If an error condition occurs, cmdmsg is assigned a explanatory message. Otherwise, cmdmsg is unchanged. |
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arctica
Joined: 10 Sep 2006
Posts: 148
Location: United Kingdom
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| Posted: Thu Jan 30, 2025 3:44 pm Post subject: |
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| Thanks for the information on cmdmsg Ken, that helps to follow the logic. |
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DanRRight
Joined: 10 Mar 2008
Posts: 2959
Location: South Pole, Antarctica
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| Posted: Thu Jan 30, 2025 4:04 pm Post subject: |
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I always thought that this error is an indication and bad example of users being lazy procrastinators not reporting bugs some of which are deeply hidden and living for centuries not exposed. This bug will outlive us all together. Impression is that the developers also tried to find out why this happening and seems found nothing suspicious.
And the pure EXECUTE_COMMAND_LINE not just does not work sometimes, it can do the whole flurry of unimaginable things. That clearly is one of those proverbial "devilry" cases cured only with the large amount users and their active reporting.
Meantime as usually we have only workarounds... workarounds.
The only way EXECUTE_COMMAND_LINE finally started working amicably in my cases was when Paul ones suggested to use it in a subroutine isolated like this
| Code: |
subroutine LaunchH5dump(iThread)
call EXECUTE_COMMAND_LINE(text256, exitstat=ierr4)
if(ierr4.ne.0) then
call sound@(2000,1)
print*,'Sound 2000 error launching h5dump in thread . text256=', trim(text256), iThread
endif
end subroutine |
and then launch it via thread launcher which is calling this subroutine
| Code: |
ii = START_THREAD@(LaunchH5dump,1)
call wait_for_thread@ (0) |
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arctica
Joined: 10 Sep 2006
Posts: 148
Location: United Kingdom
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| Posted: Wed Feb 12, 2025 6:05 pm Post subject: |
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Quick update.
Came across an old bit of code I had and this command works without issue for a long string:
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call cissue@('grdinfo xyz-test-gmt.grd -C | ' // &
'gawk "{xmin=$2; xmax=$3; ymin=$4; ymax=$5; nx=$10; ny=$11};' // &
'{print xmin, xmax, ymin, ymax, 2*nx, 2*ny}" > nxy.txt', fail) |
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simon
Joined: 05 Jul 2006
Posts: 313
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| Posted: Tue Dec 16, 2025 12:44 am Post subject: |
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I cannot get this to produce any output:
| Code: |
Program p
Call Execute_Command_Line ( 'ver > testver.txt', Wait=.true. )
End Program p |
not even with an attempt to follow Dan's suggestion:
| Code: |
! Module m
Contains
Subroutine s(ithread)
Integer(7) :: ithread
Call Execute_Command_Line ( 'ver > testver3.txt', Wait=.true. )
End Subroutine s
End Module m
Program p
Use m
Include <windows.ins>
Integer(7) :: i,j
Call System ( 'ver > testver1.txt' )
Call Execute_Command_Line ( 'ver > testver2.txt', Wait=.true. )
i = start_thread@( s, j )
Call wait_for_thread@ ( 0 )
End Program p
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mecej4
Joined: 31 Oct 2006
Posts: 1935
Location: USA
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| Posted: Tue Dec 16, 2025 4:11 am Post subject: running a command and redirecting its output |
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See if the following program, which is much simpler than what you tried, meets your needs:
| Code: |
Program p
call system('ver>testver2.txt')
End Program p
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simon
Joined: 05 Jul 2006
Posts: 313
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| Posted: Tue Dec 16, 2025 6:34 am Post subject: |
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| Yes, that does work, but my understanding is that System is a FTN95 extension (although I could not find any documentation for it), and I need the code to work across different compilers. Of course, I can, and did, implement a conditional compilation, but if Execute_Command_Line does not work it should at the least return an error, and when using Exitstat I get a return of 0. |
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PaulLaidler
Site Admin
Joined: 21 Feb 2005
Posts: 8316
Location: Salford, UK
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| Posted: Tue Dec 16, 2025 9:20 am Post subject: |
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The following works..
| Code: |
| Call Execute_Command_Line ( 'cmd /c ver > testver3.txt', Wait=.true. ) |
The prefix "cmd /c" is currently needed for the command "ver" but not for "dir". I have not tested other commands.
In the next release of the library, "cmd /c" will be prepended if it is not already supplied and this ought to work for all commands.
"Wait=.true." is the default and can be omitted. |
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simon
Joined: 05 Jul 2006
Posts: 313
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| Posted: Tue Dec 16, 2025 7:40 pm Post subject: |
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Great - that's what I need.
On a related topic, prefixing with cmd /c also gets the following to work:
| Code: |
| Call execute_command_line ( 'cmd /c echo %CD%' ) |
I was trying to get the current directory from the environment variable CD, but the following does not work:
| Code: |
| Call get_environment_variable ( 'CD', cdir ) |
The failure, according to other forums, has little to do with the compiler, and more to do with whether CD is properly defined as an environment variable. Regardless, given that the execute_command_line works, the output can be redirected and then the current directory can then be read easily. |
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