Well, for starters -- it's a pretty silly thing to do, either way. Why do echo "`command`" when you could just do command ?
But the difference is, quotes prevent a string from splitting on whitespace. Spaces, tabs and newlines all count as whitespace. If you do VAR="a b c", and use $VAR without putting it into quotes, the shell will split it in three.
So, quoted, it ends up being:
And the unquoted way ends up being:
This is also one of many reasons why for LINE in `command` is a poor idea. It splits on whitespace, not lines.
Hi,
I've modified the syslogd source to include a thread that will keep track of a timer(or a timer thread). My intention is to check the file size of /var/log/messages in every one minute & if the size is more than 128KB, do a echo " " > /var/log/messages, so that the file size will be set... (7 Replies)
So in my shell i execute:
{ while true; do echo string; sleep 1; done } | read line This waits one second and returns.
But
{ while true; do /bin/echo string; sleep 1; done } | read line continues to run, and doesn't stop until i kill it explicitly.
I have tried this in bash as well as zsh,... (2 Replies)
Hello All
Nice to meet you all here in this forum,
it's my 1rst time here
i'm asking about a little issue that i face
i added a ksh script that echo " please insert your name " and store the output to a login.log file.
the script is working fine with normal telnet
but Xstart is not working... (8 Replies)
echo `echo ` doesn't echoes anything. And it's logic. But
echo `echo `echo ` ` does echoes "echo". What's the logic of it? the `echo `echo ` inside of the whole (first) echo, echoes nothing, so the first echo have to echo nothing but echoes "echo"
(too much echoing :P):o (2 Replies)
Hello,
On a HP-UX 10.20 server I've executed something similar to this command:
# echo 'selall;info;wait;infolog;view;done' | /usr/sbin/cstm
But it returns sometype of "argument list too long" error.
I suppose there is a way to fix it by using xargs but I can't figure it out.
Any... (7 Replies)
Hello, I have a simple(I think) question!
Although simple, I have been unable to resolve it, so I hope someone can help! OK, here it is:
1)I have an awk script that prints something, such as:
awk '{print $2}' a > x
so x might hold the value of say '10'
2)Now, I just want to check to see if... (4 Replies)
Hi guys,
I have a shell script where I have the following:
for i in ad0 ad1
do
gpart create -s gpt $i || echo "Cannot create GPT partition on "$i". Exiting ..."
gpart add -s 128 -t freebsd-boot $i || echo "Cannot add freebsd-boot partition on "$i". Exiting ..."
gpart add -s 4G -t... (2 Replies)
Hi Folks,
As per the subject, the following command is not working as expected.
echo $variable | mail -s "subject" "xxx@xxx.com"
Could anyone figure it out whats wrong with this. I am using AIX box.
Regards, (2 Replies)
I came across and unexpected behavior with redirections in tcsh. I know, csh is not best for redirections, but I'd like to understand what is happening here.
I have following script (called out_to_streams.csh):
#!/bin/tcsh -f
echo Redirected to STDOUT > /dev/stdout
echo Redirected to... (2 Replies)
Discussion started by: marcink
2 Replies
LEARN ABOUT PHP
exec
EXEC(3) 1 EXEC(3)exec - Execute an external programSYNOPSIS
string exec (string $command, [array &$output], [int &$return_var])
DESCRIPTION exec(3) executes the given $command.
PARAMETERS
o $command
- The command that will be executed.
o $output
- If the $output argument is present, then the specified array will be filled with every line of output from the command. Trailing
whitespace, such as
, is not included in this array. Note that if the array already contains some elements, exec(3) will append
to the end of the array. If you do not want the function to append elements, call unset(3) on the array before passing it to
exec(3).
o $return_var
- If the $return_var argument is present along with the $output argument, then the return status of the executed command will be
written to this variable.
RETURN VALUES
The last line from the result of the command. If you need to execute a command and have all the data from the command passed directly back
without any interference, use the passthru(3) function.
To get the output of the executed command, be sure to set and use the $output parameter.
EXAMPLES
Example #1
An exec(3) example
<?php
// outputs the username that owns the running php/httpd process
// (on a system with the "whoami" executable in the path)
echo exec('whoami');
?>
NOTES
Warning
When allowing user-supplied data to be passed to this function, use escapeshellarg(3) or escapeshellcmd(3) to ensure that users can-
not trick the system into executing arbitrary commands.
Note
If a program is started with this function, in order for it to continue running in the background, the output of the program must be
redirected to a file or another output stream. Failing to do so will cause PHP to hang until the execution of the program ends.
Note
When safe mode is enabled, you can only execute files within the safe_mode_exec_dir. For practical reasons, it is currently not
allowed to have .. components in the path to the executable.
Warning
With safe mode enabled, the command string is escaped with escapeshellcmd(3). Thus, echo y | echo x becomes echo y | echo x.
SEE ALSO system(3), passthru(3), escapeshellcmd(3), pcntl_exec(3), backtick operator.
PHP Documentation Group EXEC(3)