Sorry, but I think there is a more elegant way: use the "${....:=...}" variable expansion. The expression "${var:=defaultvalue}" evaluates to the value of $var if $var is non-null (non-zero) or to defaultvalue otherwise. Here is an example:
hi,
am a new learner to shell programming.
i have a script which will prompt for user to key in their name & display their name afterwards.
script
=====
echo "Pls enter your name:"
read name
echo "Your name is $name."
output
=====
Pls enter your name:
Bob
Your name is Bob.
what... (2 Replies)
Hi guys,
I am new to AWK and unix scripting. Please see below my problem and let me know if anyone you can help.
I have 2 input files (example given below)
Input file 2 is a standard file (it will not change) and we have to get the name (second column after comma) from it and append it... (5 Replies)
i want to get input and depending on it create new commands for input to expect.
But problem is that after giving date or month as 01-09 it is interpretation as 1-9
echo -n "ENTER DATE "
read d1
echo -n "ENTER MONTH "
read m1
echo -n "ENTER YEAR"
read y1
o=1
i=1
d2=`expr $d1... (1 Reply)
Hello,
I'm trying to figure out how best to approach this script, and I have very little experience, so I could use all the help I can get. :wall:
I regularly need to delete files from many directories.
A file with the same name may exist any number of times in different subdirectories.... (3 Replies)
HI
i have written a script to ask input from the user.
this script should promote the user for y/n input. if user enters anyother input then y/n
the script promotes him again. this below code is working fine for all the cases.
except for space and enter " if i give space and enter it is... (2 Replies)
hi all
i'm new in shell scripting and now i'm working on project and i wanna make a function take input from user and test it's datatype then if correct write it to file
i wounder what is the best way to do this ?
can i use awk ?
edit by bakunin: Please give your threads a meaningful... (5 Replies)
Dear Friends,
I am looking for a shell script to merge input files into one file .. here is my idea:
1st paramter would be outfile file (all input files content)
read all input files and merge them to input param 1
ex: if I pass 6 file names to the script then 1st file name as output file... (4 Replies)
Just started learning Unix and received my first assignment recently. We haven't learned many commands and honestly, I'm stumped. I'd like to receive assistance/guidance/hints.
1. The problem statement, all variables and given/known data:
How do I write a shell script that takes in a file or... (4 Replies)
I am trying to allow a user to enter in text and then store that text in a variable $gene to run in an awk command in which those values are used to run some calculations. I am getting syntax errors however, when I try. Thank you :).
The awk runs great if it is a pre-defined file that is used,... (7 Replies)
Discussion started by: cmccabe
7 Replies
LEARN ABOUT PHP
unset
UNSET(3) 1 UNSET(3)unset - Unset a given variableSYNOPSIS
void unset (mixed $var, [mixed $...])
DESCRIPTION unset(3) destroys the specified variables.
The behavior of unset(3) inside of a function can vary depending on what type of variable you are attempting to destroy.
If a globalized variable is unset(3) inside of a function, only the local variable is destroyed. The variable in the calling environment
will retain the same value as before unset(3) was called.
<?php
function destroy_foo()
{
global $foo;
unset($foo);
}
$foo = 'bar';
destroy_foo();
echo $foo;
?>
The above example will output:
bar
To unset(3) a global variable inside of a function, then use the $GLOBALS array to do so:
<?php
function foo()
{
unset($GLOBALS['bar']);
}
$bar = "something";
foo();
?>
If a variable that is PASSED BY REFERENCE is unset(3) inside of a function, only the local variable is destroyed. The variable in the
calling environment will retain the same value as before unset(3) was called.
<?php
function foo(&$bar)
{
unset($bar);
$bar = "blah";
}
$bar = 'something';
echo "$bar
";
foo($bar);
echo "$bar
";
?>
The above example will output:
something
something
If a static variable is unset(3) inside of a function, unset(3) destroys the variable only in the context of the rest of a function. Fol-
lowing calls will restore the previous value of a variable.
<?php
function foo()
{
static $bar;
$bar++;
echo "Before unset: $bar, ";
unset($bar);
$bar = 23;
echo "after unset: $bar
";
}
foo();
foo();
foo();
?>
The above example will output:
Before unset: 1, after unset: 23
Before unset: 2, after unset: 23
Before unset: 3, after unset: 23
PARAMETERS
o $var
- The variable to be unset.
o $...
- Another variable ...
RETURN VALUES
No value is returned.
EXAMPLES
Example #1
unset(3) example
<?php
// destroy a single variable
unset($foo);
// destroy a single element of an array
unset($bar['quux']);
// destroy more than one variable
unset($foo1, $foo2, $foo3);
?>
Example #2
Using (unset) casting
(unset) casting is often confused with the unset(3) function. (unset) casting serves only as a NULL-type cast, for completeness. It
does not alter the variable it's casting.
<?php
$name = 'Felipe';
var_dump((unset) $name);
var_dump($name);
?>
The above example will output:
NULL
string(6) "Felipe"
NOTES
Note
Because this is a language construct and not a function, it cannot be called using variable functions.
Note
It is possible to unset even object properties visible in current context.
Note
It is not possible to unset $this inside an object method since PHP 5.
Note
When using unset(3) on inaccessible object properties, the __unset() overloading method will be called, if declared.
SEE ALSO isset(3), empty(3), __unset(), array_splice(3).
PHP Documentation Group UNSET(3)