Forum OpenACS Q&A: Error: nsd.tcl: error reading output from command: interrupted system call

I have worked around this problem by defining my own exec proc called dc_exec and in there redirecting the output of program to be executed to a file and then reading the contents back in and returning it.

Unfortunately I've had to go through the all the .tcl files and change exec to dc_exec. Here's the procedure:

# this is a workaround for a problem on FreeBSD where the tcl exec function

# fails half the time with the message

# error reading output from command: interrupted system call

# which as far as I can see is a problem with the output of whatever program

# The workaround is to redirect the output to a file and then read in the file

# and return the output in the normal way

# I have a sequence in the database for unique tmp filenames

#

proc dc_exec {prog_name args} {



# Generate a new unique filename for the output of this command

set db [ns_db gethandle]

set next_id [database_to_tcl_string $db "select nextval('tmp_fname_sequence')"]

ns_db releasehandle $db

set tmpFName [ad_parameter PhotoDataRoot photodb]/dc-exec-$next_id



# Run the command - note the eval here splits the args

set command "exec $prog_name $args > $tmpFName"

eval $command



# Read and return the output of the command - clean up file

set fId [open $tmpFName]

set return_string [read $fId]

close $fId

file delete $tmpFName return $return_string

}


proc dc_exec {prog_name args} {

# Generate a new unique filename for the output of this command
set tmpFName [ad_parameter PhotoDataRoot photodb]/dc-exec-[ns_thread getid]

# Run the command - note the eval here splits the args
set command "exec $prog_name $args > $tmpFName"
eval $command

# Read and return the output of the command - clean up file
set fId [open $tmpFName]
set return_string [read $fId]
close $fId
file delete $tmpFName
return [string trimright $return_string]
}