Checking ksh script syntax

Shell Programming and Scripting
1

To check a bash script syntax without executing it we use:

bash -n scriptname

What should be the equivalent command for checking a ksh script?

2 
ksh -n scriptname
3

I have a script:

[root@wiki ~]# cat load_avg_alert.sh
#!/bin/ksh


UPTIME=`uptime|grep -o 'load.*'|sed 's/[,|:]//g'`

avg1min=`echo "$UPTIME"|grep -o "load average.*"|awk '{print $3}'`
avg5min=`echo "$UPTIME"|grep -o "load average.*"|awk '{print $4}'`
avg15min=`echo "$UPTIME"|grep -o "load average.*"|awk '{print $5}'`

When i run
 ksh load_avg_alert.sh

I get no error as output.

But when i run

ksh -n load_avg_alert.sh

i get the following error:

load_avg_alert.sh: warning: line 4: `...` obsolete, use $(...)
load_avg_alert.sh: warning: line 6: `...` obsolete, use $(...)
load_avg_alert.sh: warning: line 7: `...` obsolete, use $(...)
load_avg_alert.sh: warning: line 8: `...` obsolete, use $(...)
load_avg_alert.sh: warning: line 10: `...` obsolete, use $(...)
load_avg_alert.sh: warning: line 12: `...` obsolete, use $(...)

Why is that?

4

These are warnings not errors. They probably refer to obsolete syntax that still works but has been superceded. By the look of it you have code that use backticks when: -

$(...)

would be better.

5

Ok got it

6

It's justa that the backticks are a bit obsolete. It's better tu use $(...). 2 good reasons:

  1. The command substitutions can be nested.
  2. The script is more readable.
    But it's not an error !
7

Command substitution can also be nested using backtick.

8

example:

VAR=$(echo "Now it is $(date)")
echo "$VAR"
9

thanks