topic Re: script doesn't execute the command but echo is okay in Operating System - HP-UX

script doesn't execute the command but echo is okay

kholikt — Sat, 05 Mar 2011 08:47:23 GMT

Hi,

I have tried this couple of times but still not sure why. The echo output show the command syntax is correct but if I treat the CMD as a command to execute it directly, the set -x show it has some extra character on it and this will cause the command to fail.

set -x
SERVERGROUP="myserver 1:myserver_2"
CLNID=1
IFS=:
for i in $SERVERGROUP
do
cg_grp="${cg_grp} '$i' $CLNID"
done
CMD="mycommand -a -d -c"$cg_grp" -o"
echo $CMD
$CMD

++ SERVERGROUP='myserver 1:myserver_2'
++ CLNID=1
++ IFS=:
++ for i in '$SERVERGROUP'
++ cg_grp=' '\''myserver 1'\'' 1'
++ for i in '$SERVERGROUP'
++ cg_grp=' '\''myserver 1'\'' 1 '\''myserver_2'\'' 1'
++ CMD='mycommand -a -d -c '\''myserver 1'\'' 1 '\''myserver_2'\'' 1 -o'
++ echo 'mycommand -a -d -c '\''myserver 1'\'' 1 '\''myserver_2'\'' 1 -o'
mycommand -a -d -c 'myserver 1' 1 'myserver_2' 1 -o
++ 'mycommand -a -d -c '\''myserver 1'\'' 1 '\''myserver_2'\'' 1 -o'

Correct command should be
mycommand -a -d -c 'myserver 1' 1 'myserver_2' 1 -o

Re: script doesn't execute the command but echo is okay

Jose Mosquera — Sat, 05 Mar 2011 10:09:20 GMT

Hi,

When you try to executes $CMD. This "mycommand" is other script? Yes, then:
1.- Have enought execution permissions?
2.- Must begging with:
./mycommand...
-or-
sh mycommand...
This last one depend of shell interpreter that you are using (sh, ksh, etc).

Rgds.

Re: script doesn't execute the command but echo is okay

kholikt — Sat, 05 Mar 2011 10:22:37 GMT

a quick and dirty fix of course is to put the command in a temporary file and run that file as script.

echo $CMD > tmp_cmd
chmod u+x tmp_cmd
./tmp_cmd
cg_grp=""
rm -f tmp_cmd

Re: script doesn't execute the command but echo is okay

kholikt — Sat, 05 Mar 2011 10:35:39 GMT

mycommand is just a binary and yes I have the permission.

Re: script doesn't execute the command but echo is okay

kholikt — Sat, 05 Mar 2011 10:36:15 GMT

quick and dirty I tired the following it will work

echo $CMD > tmp_cmd
chmod u+x tmp_cmd
./tmp_cmd
cg_grp=""
rm -f tmp_cmd

Re: script doesn't execute the command but echo is okay

Matti_Kurkela — Sat, 05 Mar 2011 10:50:34 GMT

Looks like the "set -x" output uses single quotes to indicate expansion results, somehow. Which shell are you using to run this?

Because you're setting IFS=:, the $CMD is not expanded into command + arguments for execution in the normal way.

The normal way would be:
$0 (the command to execute) = mycommand
$1 = -a
$2 = -d
$3 = -c
$4 = 'myserver 1'1
$5 = 'myserver_2'1
$6 = -o

Because you've set IFS=:, space isn't a separator character anymore, and you're getting:
$0 = mycommand -a -d -c 'myserver 1'1 'myserver_2'1 -o

which obviously is unlikely to be found in the PATH as an executable command.

I would suggest getting rid of the custom IFS setting as soon as it is not needed any more: IFS is a classic way to shoot yourself in the foot.

set -x
SERVERGROUP="myserver 1:myserver_2"
CLNID=1
IFS=:
for i in $SERVERGROUP
do
cg_grp="${cg_grp} '$i' $CLNID"
done
unset IFS #resume standard behavior
CMD="mycommand -a -d -c"$cg_grp" -o"
echo $CMD
$CMD

My test of this modified script fragment produced this result. If I understand correctly, this is what you wanted:

+ SERVERGROUP=myserver 1:myserver_2
+ CLNID=1
+ IFS=:
+ cg_grp= 'myserver 1' 1
+ cg_grp= 'myserver 1' 1 'myserver_2' 1
+ unset IFS
+ CMD=mycommand -a -d -c 'myserver 1' 1 'myserver_2' 1 -o
+ echo mycommand -a -d -c 'myserver 1' 1 'myserver_2' 1 -o
mycommand -a -d -c 'myserver 1' 1 'myserver_2' 1 -o
+ mycommand -a -d -c 'myserver 1' 1 'myserver_2' 1 -o
ifstest.sh: 1: mycommand: not found

MK

Re: script doesn't execute the command but echo is okay

Jose Mosquera — Sat, 05 Mar 2011 11:00:56 GMT

Hi,

Instead of execute $CMD try directly:
mycommand -a -d -c $cg_grp -o

Rgds.

Re: script doesn't execute the command but echo is okay

James R. Ferguson — Sat, 05 Mar 2011 14:13:41 GMT

Hi:

> Matiti: IFS is a classic way to shoot yourself in the foot.

This is very true. In shell's I like to do:

...
OLDIFS=${IFS}
IFS=":"
...
IFS=${OLDIFS}
...

The default value for IFS consists of a space, a tab and a newline character.

Regards!

...JRF...