Shell script declare declaring variables

Linux bash Shell's declare

declare or typeset built-in commands (which are exactly the same) can be used to constrain the properties of a variable. This is a way to use a less restrictive definition type in some programming languages. Command declare is only available after Bash version 2. The command typeset can also be run in the Ksh script .

Declare/typeset Options

- R Read-only

#!/bin/bashdeclare-r Haha=leafecho $hahahaha =whatecho What's $haha?

• The results of the operation are as follows and cannot be modified until the declaration is visible.
  

• [Email protected] mnt]#./declare2.sh
  Leaf
  ./declare2.sh:line 11:haha:readonly Variable
  What's the leaf?
  
  -I shaping

• 
  

• #!/bin/bashdeclare-i numnum=1echo num= "$num" Num=2echo num= "$num" Num=threeecho num= "$num" num=1num= $num +1echo num= "$ Num

• [Email protected] mnt]#./declare3.sh
  Num=1
  num=2
  Num=0
  num=2
  
  
  

• #!/bin/bashn=10/5echo n= $ntypeset-i n//and declare an effect echo n= $n//Note here the output N=10/5echo n= $n

• 
  [Email protected] mnt]#./declare4.sh

• N=10/5
  N=10/5//Note the output here, you can see the previous declared variables or the variable, declare need to declare again.
  n=2

• 
  

• #!/bin/bashfoo () {Declare foo= "bar" echo "Now foo= $FOO" return 20}bar () {fooif [$?-eq];thenecho "$FOO" Else echo nonof i} Bar

  
  

[Email protected] mnt]#./declare1.sh
Now Foo=bar

As you can see, declare declares a local variable, so the function call is gone.

-F Displays all previous functions followed by the function name specified to display a function

  7 #!/bin/bash  8  Foo ()   9 { 10 declare foo= "bar"  11 echo  "now foo= $FOO"   12 return 20 13 } 14 bar ()  15 { 16 foo 17 if  [ $? -eq 20 ];then 18 echo  "$FOO"  19 else 20      echo nono 21 fi 22 } 23 bar 24 declare -f  25 declare -f foo 

[Email protected] mnt]#./declare1.sh
Now Foo=bar

Bar ()
{
Foo
If [$?-eq 20]; Then
echo "$FOO";
Else
Echo Nono;
Fi
}
Foo ()
{
DECLARE foo= "Bar";
echo "Now foo= $FOO";
return 20
}// declare-f results
Foo ()
{
DECLARE foo= "Bar";
echo "Now foo= $FOO";
return 20
} //declare-f foo results

Shell script declare declaring variables