Programming :: Detect Pipe From Running C Program?
Jan 24, 2009
I'm looking for a way to detect whether or not a program has been called from pipe, e.g.
Code:
whatever | my_program
versus simply just being exectuated directly:
Code:
my_program
Why? In the first case, I want to run the program non-interactively, and in the latter case I want to print out user-friendly messages. I've been thinking along the lines of some check I haven't yet found, like:
Code:
if( stream_buffer_is_not_empty() )
print_interactive_messages();
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Sep 23, 2009
i wanted to capture the stdout and stdin of a child process within a parent so that any output of child is sent to the parent and any input taken from the parent. code is simple enough and i have followed all code guidlines on the internet (some guidlines do differ also) my select call either hangs if i do not give a tmeout and with a timeout it returns 0 descriptors to be written to or read from:
below is the simple code for parent:
int main(void)
{
int outfd[2];
int infd[2];
[code].....
why select hangs without a timeout ... why can it not detect that the pipe is write ready i.e parent can write to it ... if it does not detect tha read pipe as having data...
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Mar 2, 2011
I've written a simple server in linux used fork to create a FIFO pipe.The server create two FIFO pipe.One for server read data from client and write data to client.Then another pipe for client read data from server and write data to server.When the server read data from a client used server-pipe and then write data to client.But ,if the client no read open the pipe,the server side write will be crashed because of a broken-pipe SIGPIPE. How to check whether the read side is opened?Or,how to catch the SIGPIPE,and then my server will still execute on,not crashed!!
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Jul 19, 2011
how to detect if a file is being opened by any application so that i can block it just before opening it... Actually i am working on android and using iNotify in JNI to detect the OPENING of a file...but the file is getting opened before the iNotify detects it..and therefore its displaying the contents of the file unmodified .. The actual requirement is that if anyone is trying to open the file it should be modified by my program and then the modified file should be opened.
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Mar 11, 2009
write a C program to detect whether the Ethernet cable is plugged or unplugged. I found out by using a command "nm-tool" in Linux terminal will show me whether a Ethernet cable is plugged or not. If Ethernet cable is plugged, in the device part of eth0, the Hardware Link of Wired Settings will indicate a "yes" and "no" if no Ethernet cable. Hence, in my previous code, I use one function called popen to read the state as shown below:
PHP Code:
[code]....
However, now my project wish to not use the NetworkManager (where the "nm-tool" command comes from). And this gives me trouble to detect the Ethernet cable. So is there any other method for me to detect the Ethernet cable in C programming?
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Nov 17, 2008
I am trying to use perl to run a program using the eval command but the program runs infinitely, i just need it to run basically for one second, stop then give me the output. I tried using fork but it does not really work. The child process is not being killed.
my $pid = fork;
if ($pid == 0) {
my $results = `ngrep etc...`;
[code]...
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Sep 18, 2010
i want to run c graphics program on linux for that i want to install[URL]but i dont know how to install this graphic file on linux to make it un.
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Mar 27, 2011
I have a script that calls another program/script, xxx, to run in the background. Supposedly this program at most should finish within five (5) minutes so after five (5) minutes, I run some other steps to run the script into completion. My problem is sometimes the program takes longer than five (5) minutes and this is causing problems when running the rest of the steps in the scripts. Can anyone suggest how to re-program my script. At the moment, the KSH script, i.e. test.ksh, is doing as below:
test.ksh:
.....
.....
xxx/xxx.ksh <--- program/script called by the script
sleep 300
..... run the rest of the script .....
..... problem is sometimes xxx/xxx.ksh takes longer than 300 seconds .....
..... any way that I can monitor that xxx/xxx.ksh finishes before I run .....
..... the rest of the scripts .....
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Mar 3, 2009
I would like to know if there is a linux command to verify the amount of memory used by a program. The programs I am using were compiled with gfortran.
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Mar 2, 2010
The situation is that I have an MPI-parallel fortran program. I run it and it's distributed on N processors, and each of these processes must call an external program.
This external program is also an MPI program, however I want to run it in serial, on the processor that is calling it, as if it were part of the fortran program. The fortran program waits until the external program has completed, and then continues.
The problem is that this external program seems to run on any processor, and not necessarily the (now idle) processor that called it.
how I can call the program and ensure it runs only on this processor?
Extra information that might be helpful:
If I simply run the external program from the command line (ie, type "/path/myprogram.ex <enter>"), it runs fine. If I run it within the fortran program by calling it via
CALL SYSTEM("/path/myprogram.ex")
it doesn't run at all (doesn't even start) and everything crashes. I don't know why this is.
If I call it using mpiexec:
CALL SYSTEM("mpiexec -n 1 /path/myprogram.ex")
then it does work, but I get the problem that it can go on any node.
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Sep 22, 2010
I'm trying to test whether wget is working still or not. While [ wget is still running ] <----- but how should this look please?
do
codes
done
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Jul 14, 2011
Running a program with arguments using a shell script
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Jan 13, 2010
My requirement is to save files before shutting the Linux machine down, unattended ie: when the user is not near the machine. This is done whenever the UPS battery is about to die, so that the files get saved. open-Office/text-editor applications that can be saved using keystrokes will have to be found from the running processes and keystrokes should be sent to them from a C program that was started in non-graphics stage. ie: from a C program that forks into memory as a daemon before xwindows part starts. How to I send keystrokes to a running application? (like cotrol + F and then wait and then send next set of keystrokes till the file is saved as a new file or as the same file itself), either from C program or a script?
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Jun 28, 2013
I have a java program that runs on Debian as a background processor. Yesterday the Java program stopped running. I looked at the memory usage, the system only had 5MB memory left, so my guess is that the java program ran out of memory to use.
However, after we restarted the java program, we could see that the free memory count started to go up. It kept going up from 5MB to over 400MB. The increase of memory happened slowly, when I measured it, I could see that with each minute passing by, there were a bit more memory added into the free memory pool, and meanwhile, the java background process was running.
I wonder why this would ever happen. It's as if our java program first brought the machine done because it consumed all the memories, then after restart, it starts to give back memories.
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Apr 13, 2010
In shell, I execute "./ffmpeg -f h264 - | xxx"
Now I hope use execl function to execute above operations,
I call execl("/bin/sh", "sh", "-c", "./ffmpeg -f h264 - | xxx");
but ffmpeg doesn't work, it seems that "|" pipe don't work.
how could I solve this?
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Aug 11, 2010
I understand that $! is the PID of a command. For example:
Code: #!/bin/bash
myprogram &
echo "PID of myprogram is $!"
I'd like to send the output of "myprogram" to both console and to a log file using the "tee" command but I also want to store the PID of "myprogam". Something like this:
Code: #!/bin/bash
myprogram | tee ./logfile &
echo "PID of myprogram is $!"
The problem is that $! is now the PID of "tee" rather than the PID of "myprogram".
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Feb 16, 2011
I am trying to automate some directory naming when we're manually running some scripts and are using tee to direct the output to a file (log). Right now this is what we do
Code:
./some_script.sh 2>&1 | tee /home/user/some_dir/logs/manual/some_script_20110216_1628.log
As a matter of laziness and keeping the log files consistently named, I'd like to create a function to pipe it to so that it's doing all the naming How I envision the command running
Code:
./some_script.sh 2>&1 | myfunc
And what the logfile name should look like (and in the right directory)
Code:
some_script_20110216-1628.log
I was thinking of adding a function to our profile to handle this. Just in testing I was trying to stream line right on the command line, but I'm having some difficulty in getting the name of the script that is pushing data over the pipe. Here is what I've tried
Code:
./some_script.sh 2>&1 | tee $(cd ../logs/manual; pwd)/$0_$(date +%Y%m%d)-$(date +%H%M).log
but that created a file named
"bash_20110216-1628.log"
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Apr 5, 2011
For instance, suppose I want to pipe the output of ps -A to a gtkdialog table.
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May 3, 2011
I want to pipe the output of ls in a folder to a file (lets call it test.txt) but when i do so, but when i do ls > test.txt in test.txt there is also test.txt (logical
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Apr 10, 2009
I'm doing ping between 2 RH servers through a VPN site2site tunnel and in some times I got in the result pipe 2 and another pipe 3 as I mark it in blue color below.
e.g.
64 bytes from 192.168.1.10: icmp_seq=0 ttl=128 time=0.229 ms
64 bytes from 192.168.1.10: icmp_seq=1 ttl=128 time=0.287 ms
64 bytes from 192.168.1.10: icmp_seq=2 ttl=128 time=0.278 ms
[code]....
What's the difference between pipe 2 and pipe 3 and what's the meaning of it?
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Mar 24, 2011
I want to have the output of a program go to 2 different files but not going to standard out. Is there a way to do this in bash? I know that in Z shell its really easy. omething like: Code: echo "test" >> file1 >> file2 Would work. But in Bash it doesn't seem that easy. I know that tee will send the output to 2 files but it also sends it to STDOUT.Something like:Code: echo "test" | tee -a file1 file2 Would put the word "test" in file1, file2, and STDOUT. Is there a way to just send the output to file1 and file2?
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Mar 14, 2010
I have a small program that reads stdin from a pipe using fgets. Now fgets blocks for the first line but after that it will not block.
The code, my_echo.c -
int main(int argc, char **argv) { char buf [2000] ;
char* pc ; printf("hello ") ; while (1)
{ buf[0] = (char) 0 ;
pc = fgets(buf, sizeof(buf), stdin);
if (pc != NULL) printf("%s ",buf); } return 0; }
How its called
* In terminal window 1: ./my_echo < my_fifo
* In terminal window 2: echo "1234" > my_fifo
* In terminal window 1: prints hello then 1234.
* Checking with ksysguard or top shows that my_echo is consuming 40% of CPU time.
Adding a few printf's shows that the gets is not blocking and returns a null pointer.
* In terminal window 2: echo "qwerty" > my_fifo
* In terminal window 1 qwerty prints.
I want a read function that does in fact block so my program does not tie up CPU time, read does not block.
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Oct 13, 2010
If a process forks its child and communicate with the child using pipe, do closing the write end of the pipe and terminating the writing process have the same effect?
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Oct 20, 2010
how to pipe the current directory listing into sort so that the output is the date in descending order (primary sort key). If there are multiple entries with the same date, I'd like the times sorted in ascending order. It seems simple but for some reason this isn't working:
ls -l | sort -k 6r -k 7
For some reason it doesn't seem to ever get to the second sort key when using column 6 (last modified date).
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Apr 3, 2010
I understand that the linux pipe is a buffer and that any data written to it will stay there until it is read, and if the max capacity of the buffer is reached, any additional writes will block (by default).
HOWEVER, the behavior of the pipeline below suggest that the write operations are buffered/cached before ever being written to the pipe on the client side here is write.sh, which creates 1000 byte string and writes it 100 times to stdout... the idea being that it'll block as soon as the 64kb linux pipe size is reached:
[Code]...
This is not what I was expecting: I was expected that once the capacity was reached, any reads would be followed immediately by a write to take advantage of the freed space. Instead, the blocked write operation seems to wait for some random amount of time/space to free until it unblocks and writes.
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Jul 21, 2011
I am building a python script which works same as SMTP protocol. I have build separate functions in that for each command of SMTP, and after this i have integrated all those functions in a new function named as send_mail(so that i don't have to execute every function separately for every command). Now, when i execute the script for the first time it runs successfully, but for the second time it gives the error of "BROKEN PIPE". I really can't make out how the socket is getting closed.
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Aug 12, 2010
I've written a usb device driver and a program that sends and receives data over the bulk pipe. The read function sometimes returnsI'm reading an unknown amount of data. However, using a usb tracker I can see that the correct data is being sent.The error only occurs sometimes.I expect that the read function is told to read more data that it receives it would fail and return -1, however if this was the case then every read call would fail.
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Apr 22, 2010
My question deals with me creating a name pipe (file) in the my /group directory called chat.I then have to write a script to read from the named pipe and save data into a file called chat.log until the words End of File are passed to the program.
-When I created the named pipe file (chat) I used the mknod chat p command..Is this the correct command to create a named pipe file? -Then I'm having trouble with my script and how to make it run until the words End of File are entered in. This is what I have so far.
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Jun 2, 2011
I am not able to execute a multiple sed statement using pipe filters in a variable. i am trying to extract a path from a file and then working on that path to change a few letters within the path by going through another sed statement.
the code looks like this code...
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Jul 26, 2010
I presume there is something in the JWM window manager - or Puppy Linux Lupu 5.01 itself that is conflicting with the normal loading of GMPLAYER....
I would like to know how to troubleshoot, and fix this problem if possible (even a workaround would be great).
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