Styjun

My c-shell code has to complete few concurrent background jobs before execution of some unix commands. However, somehow in code my background jobs never returns handle to unix commands.

i.e.

 $cmd1 | tee $XD/m1.log&
 $cmd2 | tee $XD/m2.log&
 $cmd3 | tee $XD/m3.log&
 $cmd4 | tee $XD/m4.log&

All 4 commands mentioned above generate 4 different files named $L1,$L2,$L3 and $L4 (example: setenv L1 $XD/div.txt etc.). I need to merge all of these files after removing the first line from them so have used following logic. But seems like sed command never gets executed

 wait $!
 echo "Job completed"
 sed -i '1d' $L2
 sed -i '1d' $L3
 sed -i '1d' $L4
 cat $L1 $L2 $L3 $L4 >> $L

Could you please help me to make then executes post background jobs?

tried

if (! -e $L4 ) then 
 if ( -f $L4 ) then 
 wait $!
 echo "Job completed"
 sed -i '1d' $L2
 sed -i '1d' $L3
 sed -i '1d' $L4
 cat $L1 $L2 $L3 $L4 >> $L
 endif
endif

but didn't help either.

 $cmd1 | tee $XD/m1.log&
 $cmd2 | tee $XD/m2.log&
 $cmd3 | tee $XD/m3.log&
 $cmd4 | tee $XD/m4.log&

 if (! -e $L4 ) then 
 if ( -f $L4 ) then 
 wait $!
 echo "Job completed"
 sed -i '1d' $L2
 sed -i '1d' $L3
 sed -i '1d' $L4
 cat $L1 $L2 $L3 $L4 >> $L
 endif
 endif

Expected results would be to generate $L file ($XD/final.txt), which would happen only when script will be back to 2nd half section containing sed command.

Short answer, just use:

wait

wait without any parameter wait will wait for all children processes. $! is pid of the last background process started so wait $! will wait only for process last child process.

Long answer, full script edited:

#!/bin/env tcsh
set cmd1 = 'printf headernline11nline12n'
set cmd2 = 'printf headernline21nline22n'
set cmd3 = 'printf headernline31nline32n'
set cmd4 = 'printf headernline41nline42n'
set XD = '.'
set L = "$XD/m.log"
set L1 = "$XD/m1.log"
set L2 = "$XD/m2.log"
set L3 = "$XD/m3.log"
set L4 = "$XD/m4.log"

touch "$L" "$L1" "$L2" "$L3" "$L4" || exit (1)
( $cmd1; sleep 5 ) | tee "$L1" &
( $cmd2; sleep 2 ) | tee "$L2" &
( $cmd3; sleep 4 ) | tee "$L3" &
( $cmd4; sleep 3 ) | tee "$L4" &
wait
echo "Job completed"
cat "$L1" > "$L"
sed '1d' "$L2" >> "$L"
sed '1d' "$L3" >> "$L"
sed '1d' "$L4" >> "$L" 

exit (0)

Test:

% ./user3093942.tcsh
[1] 1542 1543
header
line11
line12
[2] 1545 1546
header
line21
line22
[3] 1548 1549
header
line31
line32
[4] 1551 1552
header
line41
line42
[4] + Done ( $cmd4; sleep 3 ) | tee ./m4.log
[3] + Done ( $cmd3; sleep 4 ) | tee ./m3.log
[2] + Done ( $cmd2; sleep 2 ) | tee ./m2.log
[1] + Done ( $cmd1; sleep 5 ) | tee ./m1.log
Job completed
% cat ./m.log
header
line11
line12
line21
line22
line31
line32
line41
line42