pclose hangs in multi-thread program

Hi Guys

i met a problem when use popen and pclose, the child command process "sh -c ifconfig | sed -n '/eth1/,$p' | sed -n '1,8p' | grep 'inet addr' | awk '{print $2}' will never exit and cost CPU high usage after several days. i think two possible reason may lead to this problem:
1) pclose may not terminate the child process successfully and hanged.
2) command "sh -c ifconfig |..."is not executed successfully. but i try this command again, it works normal.
i perfer to the first reason, but i am not sure it and don't know why.
Could anyone can give some advice? Thank you!

the code is as follows:

  sprintf(command, "ifconfig | sed -n '/s/,$p' | sed -n '1,8p' | grep 'inet addr' | awk '{print $2}'", "eth1");
    if ((fd = popen(command, "r")) == NULL)
    {
        ret = -1;
        goto END;
    }

    while (fgets(value, 1024, fd))
    {
        value[strlen(value) - 1] = 0;
        ret = 0;
        .....
        goto END;
    }

END:
    if (fd != NULL)
    {
        pclose(fd);    }

top commands information: please note the STAT is RUN.

PID  PPID USER     STAT   VSZ %VSZ CPU %CPU COMMAND
10183  2664 root     R     3388  0.3   1 49.7 sh -c ifconfig | sed -n '/eth1/,$p' | sed -n '1,8p' | grep 'inet addr' | awk '{print $2}'

please use [code]here comes your code[/code] to keep formatting
use:

sprintf(command, "ifconfig eth1 | sed |sed ....")

and finally avoid using chains like sed|sed|grep|awk, because usually that commands can be implemented in one single script
What language did you use?

Originally Posted by pan64 please use [code]here comes your code[/code] to keep formatting use: sprintf(command, "ifconfig eth1 | sed |sed ....") and finally avoid using chains like sed|sed|grep|awk, because usually that commands can be implemented in one single script What language did you use?

Thank for your response, pan64.
C language used for this API. Do you mean sed|grep|awk may lead to this problem? but popen already create one process to execute these commands.

one problem can be you close the socket before eof (looks like you goto end after the first 1024 bytes) and therefore there can be something still running. Also stren(value) may or may not work (depending on the content), but value[strlen(value) - 1] = 0; is a noop, because strlen(value) will search for 0 - what you want to set.
sed|grep|awk itself will not cause that problem.

Originally Posted by pan64 one problem can be you close the socket before eof (looks like you goto end after the first 1024 bytes) and therefore there can be something still running. Also stren(value) may or may not work (depending on the content), but value[strlen(value) - 1] = 0; is a noop, because strlen(value) will search for 0 - what you want to set. sed|grep|awk itself will not cause that problem.

You give me a good clue for this problem.
because cpu high usage process is "sh -c ifconfig | ..", so i think these commands are kept executing all the time, so popen API is not exited, fget and pclose shouldn't be executed so far. i checked that parent process (PID 2664) is pending now.

i need to check what case will lead the script "sh -c ifconfig | sed -n '/eth1/,$p' | sed -n '1,8p' | grep 'inet addr' | awk '{print $2}'" not return back, ifconfig/awk/sed/grep are got from busybox v1.19.4.

If suggestion, it is very appreciated.