I am trying to provide support for coredump file generation from my rootfs ,I have modified /etc/limits file with "ulimit -c unlimited" command and "* hard core -1" ,Now when I give kill -6 $$ ,expecting core file generation but to get this core file have to run ulimit -c unlimited explicitly .
But I want it to happen automatically , no need to run ulimit -c unlimited it again in shell.
Can anybody tell me what changes I have to make for the same to happen
From a program you can use setrlimit(RLIMIT_CORE, ...) to set the core file's maximum size. To specify an infinite size pass RLIM_INFINITY.
For details on this please read here: http://manpages.debian.net/cgi-bin/man.cgi?query=getrlimit&sektion=2
Using the sysctl command you can do
sysctl kernel.core_pattern=/var/core/core.%p
to have the kernel create cores named core.<pid> in /var/core.
Adding kernel.core_pattern=/var/core/core.%p to /etc/sysctl.conf makes it permanent. (run sysctl -p to process your changes to /etc/sysctl.conf)
Besides %p (for the process id) there are other placeholders as follows (taken from here):
%% a single % character
%p PID of dumped process
%u (numeric) real UID of dumped process
%g (numeric) real GID of dumped process
%s number of signal causing dump
%t time of dump, expressed as seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC)
%h hostname (same as nodename returned by uname(2))
%e executable filename (without path prefix)
%E pathname of executable, with slashes ('/') replaced by exclamation marks ('!').
%c core file size soft resource limit of crashing process (since Linux 2.6.24)
Related
I'm running GNU - Screen (4.03.01) so I can have multiple terminals in one, and I'm looking for a good way to display live stats of my memory, so as I do things like compiling, testing programs, etc... I can see how much resources I have left.
I know there is "TOP" the performance monitor... and other similar programs, but I'm not looking for the entire active process list etc... I just want a snapshot of my memory stats that updates for example every 3-5 seconds.
I really appreciate anyone taking the time to help me with this, so thank you!
(for visualization purposes)
Screenshot:
You can use the combination of watch which repeats the specified program and displays its output and free which shows current memory usage
watch free -m
free --help
Usage:
free [options]
Options:
-b, --bytes show output in bytes
-k, --kilo show output in kilobytes
-m, --mega show output in megabytes
-g, --giga show output in gigabytes
--tera show output in terabytes
-h, --human show human-readable output
--si use powers of 1000 not 1024
-l, --lohi show detailed low and high memory statistics
-o, --old use old format (without -/+buffers/cache line)
-t, --total show total for RAM + swap
-s N, --seconds N repeat printing every N seconds
-c N, --count N repeat printing N times, then exit
--help display this help and exit
-V, --version output version information and exit
For more details see free(1).
watch --help
Usage:
watch [options] command
Options:
-b, --beep beep if command has a non-zero exit
-c, --color interpret ANSI color sequences
-d, --differences[=]
highlight changes between updates
-e, --errexit exit if command has a non-zero exit
-g, --chgexit exit when output from command changes
-n, --interval seconds to wait between updates
-p, --precise attempt run command in precise intervals
-t, --no-title turn off header
-x, --exec pass command to exec instead of "sh -c"
-h, --help display this help and exit
-v, --version output version information and exit
You could use valgrind tool Massif, I haven't tried it, but it seems to be what you are looking for.
To use massif, install valgrind then run:
valgrind --tool=massif program argument1 argument2 ...
another fast solution is script like this
while true; do
free -m
# any command for CPU stats - i didn't understand - what you really want to see, please clarify - just % of CPU usage ?
# i think this command should help you.
ps -A -o pcpu | tail -n+2 | paste -sd+ | bc
done
The other thing you can do is use htop. It displays memory usage, CPU usage per core and shows resources used by each process. Really neat but maybe not that detailed as the rest of the answers.
I'm trying to get the information on a PID via c or terminal (ideally I would like to get it both ways, multiple methods)
I have a PID and would like to figure out the time it was claimed. By claimed i mean when a program started using it. Or if a PID was reused, when the latest program that is using it, started to use it.
In Linux what I do is lstat "/proc/PID_HERE/exe" or lstat "/proc/PID_HERE/cmdline" but I cant figure out how to do this on Mac OS.
Note: I changed from stat to lstat because a single exe is being used with command line arguments to open multiple instances. So each instance gets a new pid, so I want info on that specific instance, thus on Linux I have to use lstat. So any lstat equivalent to get pid info on mac os?
I think you mean this:
ps -p <PID> -o start=
10:22am
where you substitute in your PID. The start= selects the start time and also suppresses the header line. If you want the header, use
ps -p <PID> -o start
STARTED
10:22am
Alternatively, you can get the start time formated more fully like this:
ps -p <PID> -o lstart=
Fri 26 Sep 10:22:50 2014
By the way, if you want a list of the keywords (like start and lstart above) you can either wade through the manage, or more simply, just give an invalid keyword and it will tell you all the ones it likes :-)
ps -o %rubbish
ps: %rubbish: keyword not found
ps: no valid keywords; valid keywords:
%cpu %mem acflag acflg args blocked caught comm command cpu cputime etime f flags gid group ignored
inblk inblock jobc ktrace ktracep lim login logname lstart majflt minflt msgrcv msgsnd ni nice nivcsw
nsignals nsigs nswap nvcsw nwchan oublk oublock p_ru paddr pagein pcpu pending pgid pid pmem ppid pri
pstime putime re rgid rgroup rss ruid ruser sess sig sigmask sl start stat state stime svgid svuid
tdev time tpgid tsess tsiz tt tty ucomm uid upr user usrpri utime vsize vsz wchan wq wqb wql wqr xstat
I'm trying to implement my own ps command, called psmod.
I can use linux system call and all utilities of the /proc directory.
I discovered that all directory in /proc directory with a number as their name are the processes in the system. My question is: how can I select only those processes which are active when psmod is called?
I know that in /proc/<pid>/stat there's a letter representing the current status of the process; anyway, for every process in /proc, this letter is S, that is sleeping.
I also tried to send a signal 0 to every process, from 0 to the maximumnumberofprocesses (in my case, 32768), but in this way it discovers far more processes than the ones present in /proc.
So, my question is, how does ps work? The source is a little too complicated for me, so if someone can explain me, I would be grateful.
how does ps work?
The way of learning standard utils - is to check their source code. There are several implementations of ps: procps and busybox; and busybox is smaller and it will be easier to begin with it. There is sources for ps from busybox: http://code.metager.de/source/xref/busybox/procps/. Main loop from ps.c:
632 p = NULL;
633 while ((p = procps_scan(p, need_flags)) != NULL) {
634 format_process(p);
635 }
Implementation of procps_scan is in procps.c (ignore code from inside ENABLE_FEATURE_SHOW_THREADS ifdefs for first time). First call to it will open /proc dir using alloc_procps_scan():
290 sp = alloc_procps_scan();
100 sp->dir = xopendir("/proc");
Then procps_scan will read next entry from /proc directory:
292 for (;;) {
310 entry = readdir(sp->dir);
parse the pid from subdirectory name:
316 pid = bb_strtou(entry->d_name, NULL, 10);
and read /prod/pid/stat:
366 /* These are all retrieved from proc/NN/stat in one go: */
379 /* see proc(5) for some details on this */
380 strcpy(filename_tail, "stat");
381 n = read_to_buf(filename, buf);
Actual unconditional printing is in format_process, ps.c.
So, busybox's simple ps will read data for all processes, and will print all processes (or all processes and all threads if there will be -T option).
how can I select only those processes which are active when psmod is called?
What is "active"? If you want find all processes that exists, do readdir of /proc. If you want to find only non-sleeping, do full read of /proc, check states of every process and print only non-sleeping. The /proc fs is virtual and is it rather fast.
PS: for example, normal ps program prints only processes from current terminal, usually two:
$ ps
PID TTY TIME CMD
7925 pts/13 00:00:00 bash
7940 pts/13 00:00:00 ps
but we can strace it with strace -ttt -o ps.log ps and I see that ps does read every process directory, files stat and status. And the time needed for this (option -tt of strace gives us timestamps of every syscall): XX.719011 - XX.870349 or just 120 ms under strace (which slows all syscalls). It takes only 20 ms in real life according to time ps (I have 250 processes in total):
$ time ps
PID TTY TIME CMD
7925 pts/13 00:00:00 bash
7971 pts/13 00:00:00 ps
real 0m0.021s
user 0m0.006s
sys 0m0.014s
"My question is: how can I select only those processes which are active when psmod is called?"
I hope this command will help you:
top -n 1 | awk "NR > 7" | awk {'print $1,$8,$12'} | grep R
I am on ubuntu 12.
My program gets executed like:
$./sort 1 < test.txt
sort is the program name
1 is the argument (argv[1])
and test.txt is the file I am inputting from
Is it possible to extract the name file from this? if so how?
The problem is I already wrote my whole program as if I could extract the name from the input line, so I need to be able to pass it into arguments.
Any help is appreciated,
Thanks!
You can't. The shell opens (open(2)) that file and sets up the redirect (most likely using dup2).
The only possible way would be for the shell to explicitly export the information in an environment variable that you could read via getenv.
But it doesn't always make sense. For example, what file name would you expect from
$ echo "This is the end" | ./sort 1
Though this can't be done portably, it's possible on Linux by calling readlink on /proc/self/fd/0 (or /proc/some_pid/fd/0).
eg, running:
echo $(readlink /proc/self/fd/0 < /dev/null)
outputs:
/dev/null
No you can't: the shell sends the content of test.txt to the standard input of your program.
Look at this:
sort << _EOF
3
1
2
_EOF
The < > | operators are processed by the shell, they alter standard input,output,error of the programs in the cmd line.
If you happen to run Solaris, you could parse pfiles output to get the file associated, if any, with stdin.
$ /usr/bin/sleep 3600 < /tmp/foo &
[1] 8430
$ pfiles 8430
8430: /usr/bin/sleep 3600
Current rlimit: 65536 file descriptors
0: S_IFREG mode:0600 dev:299,2 ino:36867886 uid:12345 gid:67890 size=123
O_RDONLY|O_LARGEFILE
/tmp/foo
1: S_IFCHR mode:0600 dev:295,0 ino:12569206 uid:12345 gid:67890 rdev:24,2
...
On most Unix platforms, you will also get the same information from lsof -p if this freeware is installed.
I need to send the arp of a IP to get it's mac address which is configured on different machine. I am arping this ip from a C program by "system(arping -c 3 -i eth0 ) but I see that this is hanged in there.
But if I run the same command from bash "arping -c 3 -i eth0 " it get executed successfully.
I could not understand why system command hanged in this case while the command is successfully completed when run from bash.
Thanks,
Since you said it was hanging you can try:
strace -o my_prog.strace -f ./my_prog
and then kill it after it hangs. Then you can view the strace output file my_prog.strace and try to figure out what went wrong.
You may want to look at the strace man page to see other options that you might like use -- of particular use to me are ones that make it show more data in buffer (and string) input/output.
If it's not really hanging you should check the return value from your call to system( ) and then inspect errno.
edit
Something that I just thought of that could cause a hang would be if arping was actually a link to a setuid root program that did sudo on the real arping and it is waiting on a password to be typed in, but the terminal for that program isn't set correctly.
try system("arping -c 3 -I eth0 ip-addr");
something like:
main()
{
system("arping -c 3 -I eth0 192.168.10.1");
}
Are you using any child process to execute above ?
From Definition of system() :
The system() function shall ignore the SIGINT and SIGQUIT signals, and shall block the SIGCHLD signal, while waiting for the command to terminate. The system() function shall not return until the child process has terminated.
Recommendations:
1.check on the return value of system() & take appropriate decision.
Eg: If return value is zero it means command processor is not available.If a child process cannot be created, or if the termination status for the command language interpreter cannot be obtained, system() shall return -1 and set errno to indicate the error.
2.Use complete shell commands to be executed.
Eg: system("arping -c 3 -I eth0 10.203.198.10");