Programming :: Pthreads Return Value Valid Or Not

Jun 14, 2010

I have confusion regarding pthreads return value. All in short, is the is a valid return value ?

void * myThrRoutine(void *arg)
struct myStruct **myst = (struct myStruct**) arg;
cout<<"In thread "<<(*myst)->var<<(*myst)->msg<<endl;
int x = 20;

This seems to work fine on pthread_join , but I want to ensure it is not by chance.

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Programming :: Preemption And Scheduling Of Pthreads

Feb 10, 2010

i think we can simulate preemption by using 2 different priority thread, am i true? I just try these scenario :
1. Create Thread A with priority 99 , SCHED_FIFO..
2. Create Thread B with priority 4 , SCHED_FIFO

Thread A started and doing some busy work.. I guess that Thread B wouldn't start until thread A finished, but I get thread B can run before Thread A finished (It just like a common task switching).. I'm sure my 2 thread has right priority. and if thread B is doing some work and if i yield it to thread A, it should preempt it but this doesnt happen, do someone kno wats happening?

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Programming :: Suspend Pthreads Without Condition

Jun 29, 2010

I just started with Pthreads and don't really know much about it. I want to suspend pthreads but apparently, there is no such function as pthread_suspend. but I don't understand why we need both mutex and condition to suspend and resume a pthread. Is it possible to suspend and resume it without using conditions?

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Programming :: Segfault In Program Using Pthreads

Mar 16, 2010

I am trying to write a peer to peer application in C++ using pthreads library. There are few types of nodes that run in the program. The 'beacon' nodes form the core of the network. The ordinary nodes 'join' the network by sending join requests to the beacon node. So, my program runs till the join requests and responses are received. When I try to 'connect' using connect function from the socket library, I get a segfault. I am not sure if the segfault occurs for the connect function, because sometimes the program just runs to completion. It could be an issue related to threads or memory allocation.

When I run gdb, it shows me the following:
(gdb) run b2-n00.ini
Starting program: sv_node b2-n00.ini
servant:12600> [New LWP 1]
[New LWP 2]
[New LWP 3]
[New LWP 4]
[New LWP 5]
[New LWP 6]
Before Exiting[LWP 1 exited]
procfs: fetch_registers, get_gregs line 3768, /proc/23952/lwp/1: No such file or directory.

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Programming :: Using Lock In OpenMP And Pthreads

Apr 14, 2011

I have a program that uses both Pthreads and OpenMP. Basically, 2 threads (Thread A and B) are created using Pthreads to do work, and in Thread A, OpenMP is used to parallelize a for loop.If I have a global variable that is accessed by the OpenMP threads and also Thread B, can I use the lock in OpenMP to ensure I have no race conditions?

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Programming :: Is Popen Thread Safe Via Pthreads?

Sep 17, 2010

I don't seem to find a conclusive answer to this one...."Is popen thread safe via pthreads?"

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Programming :: Related To Pthreads And Timers In POSIX Standard

Feb 17, 2010

I have created two threads:
Thread 1 and thread 2

In the main thread, i have put up a timer which generates a signal periodically when it expires, which reults in execution going to signal catcher function.when this function is invoked, under certain condition it goes to thread 1 and under another condition it goes to thread 2. The problem lies here that when it goes to thread2,i have a loop to process but it doesnt come out of the loop and hence from thread2, even though timer has expired.

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Programming :: Termios Programming - Without Removing Carriage Return / Enter Key

Jun 30, 2010

I trying to write a UART(interfacing of serial devices) to linux machine but after I execute the following code to receive data I need to enter key (carriage return).... but I don't want to remove carriage return/enter key


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Programming :: Die 'error' If (xxx) - Valid Perl?

Mar 2, 2010

I saw a wierd code in perl code recently it went kind of like this: die 'error' if (xxx); Now is that valid perl?

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Programming :: Bash Function Check For Valid IP?

Apr 16, 2010

I have been working on this way too long now...this *should* be simple. I must be missing something simple at this point.

function f_is_ip()
if [ "`echo "$1" | /bin/egrep "[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}"`" != "" ] ## Error on this line


When I echo $1 ## prints

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Programming :: MATLAB - Any Valid Free Alternatives?

Mar 2, 2010

I need MatLab for a course at the university, but it's not an open source software as all of you know, so I wanted to know if there are valid freeware alternatives. I was told to use Octave or Scilab if I didn't want to buy the license and so I would like to know what's better in terms of MatLab compatibility and ease of use, if there are any other (and maybe better) alternatives and also if there are free Simulink-like programs.

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Programming :: Else &amp; Return Values?

Oct 12, 2010

i am having two small issues with a function i have made.sorry if it is a mess, i am still learning bash.the first is calling the nonpersistssh function (second line) and assigning the return value to nonpersistdiag.the function returns 1, but nonpersistdiag seems to only contain 0. i am unsure on how to proceed.the second problem is the nested else clause on line 10. it is a syntactical error. how would i declare it correctly?

Code: function endsession(){
nonpersistdiag=$[nonpersistssh]# a function that returns an exit code
sudo /etc/init.d/ssh stop; sshdiag=$?


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Programming :: Return And Exit In C

Jun 3, 2011

What are the uses of return 0, return 1 and exit statements in C

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Programming :: Return Value From A Function?

Nov 15, 2010

On this link [URL]4 a return type is defined

return ((unsigned int)(unsigned long)base & TBASE_DEFERRABLE_FLAG);
What is the above function returning.I am not clear with definition of what is being returned in the above code.

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Programming :: What Exactly Does Echo $0 Return

Jan 18, 2010

I'm confused about what "echo $0" in a shell actually return. Consider these tests:

[root@e11apvl151 ~]# # Login shell:
[root@e11apvl151 ~]# echo $0
[root@e11apvl151 ~]# # Starting a new shell
[root@e11apvl151 ~]# bash
[root@e11apvl151 ~]# echo $0
[root@e11apvl151 ~]# screen
[root@e11apvl151 ~]# echo $0

Depending on wether the shell is a login shell, a regular shell, or a screen utility, I get different results.

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Programming :: Tell If Grep Didn't Return Anything?

Mar 15, 2011

I have a file:


I want to see if all the records in the file are present in the contents of the files of a particular directory.

Basically I want to say if grep doesn't return anything, then report.

For example in /tmp dir I have 4 files and flast 2 values (787862348 and 766428634) are present in the files of /tmp dir, but first one (979798707) is not. I want to echo that in a reporting file.

something like:

while read line
# if ! grep -rl $line /tmp
echo $line >> are_not_present
done < "myFile"

How do I achieve " if ! grep -rl $line /tmp"? That is, if the line is found by grep, then grep will print the output, but if grep does'nt find it, it will print nothing. How can I check if grep didn't find it (i.e. printed nothing)?

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Programming :: C - Return To The Beginning Of A File?

Dec 16, 2010

I'm reading a text file with fscanf using a loop until feof(inFile). How can I return to the top of the file? As in I have one loop that scans until the eof and then after it there's another loop and I want to start from the beginning of the file again scanning to the end of it. How do I get back there?

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Programming :: Echo Hello Command Does Not Return

Jan 11, 2010

I am testing the serial ports on a Single Board Computer(SBC) running Linux kernel 2.6.29. I usually do this by connecting the serial port to another PC serial port, then doing "cat /dev/ttyS0" on PC and "echo hello > /dev/ttyS0" on the SBC. However in the current system, "echo hello > /dev/ttyS0" command does not return at all! Also no characters appear on the destination port. I am running the echo command as root. The system boot messages show that the serial port in indeed /dev/ttyS0.

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Programming :: Getting Return Value From Program Ran In Background?

Mar 10, 2010

I think my title pretty much explains it. I am writing a script and I want to start a program in the background, and when that program finishes I want to check the return value to make sure there was no error.For example normal I would do something like this:

if [ ! $? -eq 0 ]; then
echo "There was an error"
exit 1

Now I want to do something like this:

PRTN=`program1 &`
if [ ! $? -eq 0 ]; then


In this case if program2 finishes before program1, I don't think the return value from program1 $PRTN would be valid at the time it is checked.

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Programming :: Pthread_create Does Not Return The PID ( Process ID)?

Aug 5, 2010

I am using pthread_create system call to create a thread. However pthread_create does not return the PID ( process ID). Is there any quick way to fınd the PID of the created thread.

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Programming :: Ofstream Return A Boolean In 'if (!ofs)'?

Mar 19, 2011

C++ code:


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Programming :: Can't Understand Return Value Of Gawk?

Mar 10, 2010

I write a little script by bash.

a=`gawk '/Iterations /{print $0}' hoge.log | gawk 'BEGIN{FS=" "}{print ($4)}'`
a=`expr 3 '*' $a`


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Programming :: Prevent Echo As Return Value?

Jan 25, 2010

I have always encountered this problem in ubuntu bash shell scripts that echo command in a function will be treated as a return value when used in a function. e.g.


The output would simply be xyz. Hence the echo seems to function as a "return" command when used in a function with a return value.

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Programming :: Does't Create Directory But Return As Value '0'?

Feb 23, 2010

$val = mkdir $directory, 755
print $val;
does't create directory but return as value '0'


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Programming :: Python: Get The Return Value Of The Last Function?

Jun 13, 2010

But it's been hell finding an answer, or I just don't know what to look for..I have a prompt that asks for a float, and if the user doesn't put in a valid number, then it should die with an error message.

def die_with_error():
print 'ERROR: You didn't specify a valid number!'


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Programming :: Init.d Script Does Not Return Prompt?

Jul 9, 2010

I have an a script in /etc/rc.d/init.d script that I would like to start and stop my sample application. I have named my script "foo", then I can start running my application my typing $ foo start but this does not return [OK] like other scripts do and does not return to shell prompt. My application is basically like this

int main()
do {
} while (1);

What is missing from my application that prevents from returning the shell prompt?

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Programming :: Pointer As Function Return Doubt?

Jul 15, 2010

I'm getting some information about C language and this session of a C book (follow the above link) is using a bad example for me. When I'm trying this example of function returning a pointer, my compiler is stating a warning that I return a pointer to a local variable. I realized that it is error prone after all this variable may be override before the function has done his execution. And the author is fooling me saying that this example is "perfectly safe". I'm wrong? There is something that I don't got yet? Sorry but this site is preventing me to post the link of book cause I'm a newbie, so a need the hack it. Just strip out the question signs:



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Programming :: Wrapping Around Functions With Different Return Types?

Feb 1, 2010

I have functions which return different data like: int, char*, double...

I also have a list of datatypes (INTEGER, TEXT, REAL...) which can be returned.

I need to map a datatype with function, which purpose is to return it. Therefore, when I determine a datatype, I would like to call the required function without doing switch all the time.

My idea is to have an array of structs like this:

struct type_func_map
int type;
void (*func_wrapper_int)(void); //void (*func_wrapper_text)(void); void (*func_wrapper_real)(void);


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Programming :: BASH Read File Once Then Return To Top?

Aug 8, 2010

I have a script that reads part of a line, delimited between the first and second intended part by a colon. Then it "chops" the part after the colon, which are words offset by commas (counting them beforehand so as to catch every word in the string's second part), like this:




single script that parses/breaks both parts of a line like this "COLORS.JPG:red,orange,yellow,green;blue,indigo,violet," so that the two parts, separated into single words (or two and three words, sometimes with spaces) can be used as single-line annotations and written to JPEG files using Exiv2. So far, I haven't been able to come up with a script that does this without one part of the total string(usually that part after the colon) becoming the first word in the second array. In other words, I look for this:


[ ]red
[ ]orange
[ ]yellow


Or vice-versa (ie, the second array winds up as a single-line "member" of the first). I think it's because I'm using a single while read loop to read the text file in which the filenames and substrings happen to be. If there's some way of reading a file once and going back to the beginning to read it again in another while loop, I haven't found it.

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Programming :: C Bool Return Values Conventions

Oct 30, 2010

I have a function that returns a boolean value, True of False. Is there any convention whether 0 = False or 0 = True? It should be obvious, 0=False, 1=True. However programs usually return 0 on success and reserve higher numbers for error values. I.e. if the program finishes successfully (function int main() finishes successfully ), it returns 0 - and that contradicts that 0 should be false.

And especially if I want a function to do some computations on parameters passed by reference and return success status. Should it return 1 (true) for success, or should it return 0 for success - like any Unix program does?

Is there any convention for this?

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