Hi,
Can the cd command be invoked using pipes???
My actual question is slightly different. I am trying to run an executable from different folders and the path of these folders are obtained dynamically from the front end. Is there a way in which i can actually run the executable... (2 Replies)
What is the difference between:
cd /tmp
tar -cf - *.txt |gzip > tmp_txt.tar.gz
and
cd /tmp
mknod pipe p
gzip < pipe > /tmp/tmp_txt1.tar.gz &
tar -cf pipe *.txt
Apart from the fact that we have to create the pipe file manually, is there any difference in the performance of the two?... (5 Replies)
Hi
How do I direct the output from ls to for example grep a in C. I am not asking for the whole shell implementation.
If I write ls|grep myfile in the shell. How is the output sent from ls to the input grep. whit int pipe(pipe); We create the pipe. I and I guess we use dup2(old... (4 Replies)
Hello all, I am trying to learn more about programming Unix pipes in C.
I have created a pipe that does od -bc < myfile | head
Now, I am trying to create od -bc < myfile | head | wc
Here is my code, and I know I might be off, thats why I am here so I can get some clarification.
#include... (1 Reply)
If a code forks 2 childs, what can the values be for the process id's of each of the child? I child pid is supposed to be 0, but what if you fork 2 of them? (5 Replies)
Hey,
Well, we're starting scripting next week for my class, and I have my command done, but I don't actually understand what the meaning is, so I was just wondering if someone could "translate" this in to words so that I might be able to do this better...
command1 | command2 | command3... (5 Replies)
I already manage to get the output that i want.. but wat if removing all the pipes and convert it 1 liner with less pipes. My command below can get the ouput that i want. i just want to remove the pipes or less pipes.
#cat file1
us-west-2a running i-3397a421... (2 Replies)
Discussion started by: kenshinhimura
2 Replies
LEARN ABOUT PHP
eval
EVAL(3) 1 EVAL(3)eval - Evaluate a string as PHP codeSYNOPSIS
mixed eval (string $code)
DESCRIPTION
Evaluates the given $code as PHP.
Caution
The eval(3) language construct is very dangerous because it allows execution of arbitrary PHP code. Its use thus is discouraged.
If you have carefully verified that there is no other option than to use this construct, pay special attention not to pass any user
provided data into it without properly validating it beforehand.
PARAMETERS
o $code
- Valid PHP code to be evaluated. The code mustn't be wrapped in opening and closing PHP tags, i.e. 'echo "Hi!";' must be passed
instead of '<? echo "Hi!"; >'. It is still possible to leave and reenter PHP mode though using the appropriate PHP tags, e.g.
'echo "In PHP mode!"; ?>In HTML mode!<? echo "Back in PHP mode!";'. Apart from that the passed code must be valid PHP. This
includes that all statements must be properly terminated using a semicolon. 'echo "Hi!"' for example will cause a parse error,
whereas 'echo "Hi!";' will work. A return statement will immediately terminate the evaluation of the code. The code will be exe-
cuted in the scope of the code calling eval(3). Thus any variables defined or changed in the eval(3) call will remain visible
after it terminates.
RETURN VALUES eval(3) returns NULL unless return is called in the evaluated code, in which case the value passed to return is returned. If there is a
parse error in the evaluated code, eval(3) returns FALSE and execution of the following code continues normally. It is not possible to
catch a parse error in eval(3) using set_error_handler(3).
EXAMPLES
Example #1
eval(3) example - simple text merge
<?php
$string = 'cup';
$name = 'coffee';
$str = 'This is a $string with my $name in it.';
echo $str. "
";
eval("$str = "$str";");
echo $str. "
";
?>
The above example will output:
This is a $string with my $name in it.
This is a cup with my coffee in it.
NOTES
Note
Because this is a language construct and not a function, it cannot be called using variable functions.
Tip
As with anything that outputs its result directly to the browser, the output-control functions can be used to capture the output of
this function, and save it in a string (for example).
Note
In case of a fatal error in the evaluated code, the whole script exits.
SEE ALSO call_user_func(3).
PHP Documentation Group EVAL(3)