With help of tips from 'here and there' , I just created a simple script to
1. declare one array and some global variables
2. read the schema names from user (user input) and want2proceed flag
3. if user want to proceed , keep reading user input schema name
4. exit the loop if user doesn't want to proceed or it reaches Maximum schema numbers (3)
5 assigns the arrays to global variable only if arrays are not null
Code:
[orcl10gdb@SVRDELLD41 schema_opt]$ cat test_while_array.sh
#declares Array and global variables
declare -a arry
cnt=0
i=0
schema1=""
schema2=""
schema3=""
# Reads schemaname and wanttoproceed flag and exit on reachig maximum schema numbers (3)
echo "Enter Schema Name 1 :"
while read schemaname
do
arry[cnt]=$schemaname
echo "Want to procede (y/n) :"
read wnt2prc
if [ $wnt2prc = "n" ];
then
break
fi
cnt=`expr $cnt + 1`
if [ $cnt -gt 2 ];
then
echo "Maximum schema number (3) Reached"
break
fi
echo "Enter Schema Name `expr $cnt + 1`:"
done
#Assigns schema names to global variables only if Not Null
if [ -n ${arry[0]} ];
then
schema1=${arry[0]}
fi
if [ -n ${arry[1]} ];
then
schema2=${arry[1]}
fi
if [ -n ${arry[2]} ];
then
schema3=${arry[2]}
fi
#echos then schema name
echo 'schema 1 '$schema1 ${arry[0]}
echo 'schema 2 '$schema2 ${arry[1]}
echo 'schema 3 '$schema3 ${arry[2]}
#while [ $i -lt $cnt ]
#do
#i=`expr $i + 1`
# Calls other sripts with arry as parameter
#done
[orcl10gdb@SVRDELLD41 schema_opt]$ sh test_while_array.sh
Enter Schema Name 1 :
schm1
Want to procede (y/n) :
y
Enter Schema Name 2:
schm2
Want to procede (y/n) :
n
schema 1 schm1 schm1
schema 2 schm2 schm2
schema 3
[orcl10gdb@SVRDELLD41 schema_opt]$
This work fine up to this stage . But wants to know any thing could be done to optimize the script or to make the script compact.
And Now I am planning to call other shell scripts with parameter as array value. Its template is also given in the above script .
The basic questions are , Is there any ..
1. change could be done to optimize the script or to make it compact ?
2. function to change the case of input schema name ?
3. technique to validate user input flag (y/n)
4. make the echo and input in the same line.
I got some new tips today especially points 2 and 4 . I almost incorporated your suggestion . Its fine now.
Code:
[orcl10gdb@SVRDELLD41 schema_opt]$ cat test_while_array.sh
#declares Array and global variables
declare -a arry
cnt=0
i=0
schema1=""
schema2=""
schema3=""
# Reads schemaname and wanttoproceed flag and exit on reachig maximum schema numbers (3)
while read -p "Enter Schema Name `expr $cnt + 1` :" schemaname
do
arry[cnt]=$schemaname
wnt2prc=""
while [ "$wnt2prc" != "n" ] && [ "$wnt2prc" != "y" ]
do
read -p "Want to procede (y/n) :" wnt2prc
done
cnt=`expr $cnt + 1`
if [ $wnt2prc = "n" ] || [ $cnt -gt 2 ]
then
if [ $cnt -gt 2 ]
then
echo "Maximum schema number (3) Reached"
fi
break
fi
done
#Assigns schema names to global variables only if Not Null
if [ -n ${arry[0]} ];
then
schema1=`echo ${arry[0]} | tr 'a-z' 'A-Z'`
fi
if [ -n ${arry[1]} ];
then
schema2=`echo ${arry[1]} | tr 'a-z' 'A-Z'`
fi
if [ -n ${arry[2]} ];
then
schema3=`echo ${arry[2]} | tr 'a-z' 'A-Z'`
fi
#echos then schema name
echo 'schema 1 '$schema1 ${arry[0]}
echo 'schema 2 '$schema2 ${arry[1]}
echo 'schema 3 '$schema3 ${arry[2]}
#while [ $i -lt $cnt ]
#do
#i=`expr $i + 1`
# Calls other sripts with arry as parameter
#done
[orcl10gdb@SVRDELLD41 schema_opt]$ sh test_while_array.sh
Enter Schema Name 1 :schm1
Want to procede (y/n) :a
Want to procede (y/n) :b
Want to procede (y/n) :y
Enter Schema Name 2 :schm2
Want to procede (y/n) :n
schema 1 SCHM1 schm1
schema 2 SCHM2 schm2
schema 3
[orcl10gdb@SVRDELLD41 schema_opt]$
But still have some doubts .
there is a section
Code:
while [ "$wnt2prc" != "n" ] && [ "$wnt2prc" != "y" ]
do
read -p "Want to procede (y/n) :" wnt2prc
done
But when I change to following (removing quotes )
Code:
while [ $wnt2prc != "n" ] && [ $wnt2prc != "y" ]
Its giving me error
Code:
[: !=: unary operator expected
Why it is ?
But another section in the existing code
The shell expands variables (preceded by $) before running the command "[" -- yes, that's right, "[" is a command! If the variable was the empty string, the [ command sees != followed by "n" and never sees the "left hand side" of the argument. So you put it in quotes. Now if the variable is NOT empty, the command works perfectly. Your while loop guarantees the variable will contain something -- either a y or n, so the second instance of [ will always have a y or n after it.
It is recommended always to use the variable with quotes especially during comparison to avoid such errors . Am I right ?
Pretty much, though analytically, you can see that the variable will contain something. However, someone can change the code that breaks that condition.... so better to always quote.
You can also do this trick, often seen in older scripts:
Code:
if [ x$var = x ];then ....
while [ ${answer}x = Yx ]; then ....
Instead of quoting the variable, you pre- or postfix something to it AND the thing you compare it to.
Thanks very much again for the lightening response .
Shell script sees to be interesting .
But still much difficult section AWK programming , though I am not pretty comfortable with normal shell script.
I am going to get stick on on to it .
The support from the sites like Unix.com may take me to the top of it
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