Bash function, for BSD Post: 302959908

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Top Forums Shell Programming and Scripting Bash function, for BSD Post 302959908 by Don Cragun on Saturday 7th of November 2015 03:27:41 PM

11-07-2015

Registered User

Quote:

Originally Posted by 1in10

I am putting this thread to shell-threads, because it is about how to make a function work properly. I need a hint for declaring a function right, it has been more than a year I did not work that straight with bash.
So my aim is to turn off the eth0 (as it would be in linux, and bge0 in bsd ), next step to generate a random mac-address as a function, turn on the bge0 device with the newly set mac-address.
My first attempt looks like this. The nasty looking sed-part is working fine.

Code:

#!bin/bash
# declare function for random mac in bsd
# turn off the ethernet device, create a random mac,
#turn on the ethernet device again

randmac() {
    openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/.$//'
    exit 1
}

ifconfig bge0 down
ifconfig bge0 hw ether $randmac
ifconfig bge0 up

exit;

May someone can give me the decisive hint, thanks in advance. Or may someone can tell me how to
install macchanger, which I use on linux. thanks!

Having a utility (or a shell function) exit with a non-zero value conventionally means that the script failed. And exit in a function definition exits the containing script; not just the function. (To leave a function and return an exit status from that function to the invoking shell script, use return instead of exit). But, the more normal case with what you're doing would be to just fall off the end of the function which will return the exit status of the last command executed by the function.

And, you treat a function as a command; not as a variable. So, try (although I have not tested this):

Code:

#!/bin/bash
# declare function for random mac in bsd
randmac() {
    openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/.$//'
}


# turn off the ethernet device, create a random mac,
# turn on the ethernet device again
ifconfig bge0 down
ifconfig bge0 hw ether $(randmac)
ifconfig bge0 up

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LEARN ABOUT DEBIAN

xunlockdisplay

XInitThreads(3) 						  XLIB FUNCTIONS						   XInitThreads(3)

NAME

       XInitThreads, XLockDisplay, XUnlockDisplay - multi-threading support

SYNTAX

       Status XInitThreads(void);

       void XLockDisplay(Display *display);

       void XUnlockDisplay(Display *display);

ARGUMENTS

       display	 Specifies the connection to the X server.

DESCRIPTION

       The XInitThreads function initializes Xlib support for concurrent threads.  This function must be the first Xlib function a multi-threaded
       program calls, and it must complete before any other Xlib call is made.	This function returns a nonzero status if initialization was suc-
       cessful; otherwise, it returns zero.  On systems that do not support threads, this function always returns zero.

       It is only necessary to call this function if multiple threads might use Xlib concurrently.  If all calls to Xlib functions are protected
       by some other access mechanism (for example, a mutual exclusion lock in a toolkit or through explicit client programming), Xlib thread ini-
       tialization is not required.  It is recommended that single-threaded programs not call this function.

       The XLockDisplay function locks out all other threads from using the specified display.	Other threads attempting to use the display will
       block until the display is unlocked by this thread.  Nested calls to XLockDisplay work correctly; the display will not actually be unlocked
       until XUnlockDisplay has been called the same number of times as XLockDisplay.  This function has no effect unless Xlib was successfully
       initialized for threads using XInitThreads.

       The XUnlockDisplay function allows other threads to use the specified display again.  Any threads that have blocked on the display are
       allowed to continue.  Nested locking works correctly; if XLockDisplay has been called multiple times by a thread, then XUnlockDisplay must
       be called an equal number of times before the display is actually unlocked.  This function has no effect unless Xlib was successfully ini-
       tialized for threads using XInitThreads.

SEE ALSO

       Xlib - C Language X Interface

X Version 11							   libX11 1.5.0 						   XInitThreads(3)

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