I'm actually doing my own shell.
I have done the following special characters:
int commande(int fin, int fout, char * com, char * param, int * bg){
// execute a command
(ex. ls –l)
int symbole;
char *mot;
pid_t pid;
symbole = parsing();
switch(symbole){
case 0: // NL
case 1: // ;
case 2: // &
case 3: // <
case 4: // >
case 5: // | (Here I have some issues when I try to redirect the output of a command).
(correspond à ctrl+D)
case 10:// Mot
default:
}
return;
}
But I have some issues to do the redirection of an output when it is piped " |", when I have two instructions that follow themselves. Indeed I have tried the following operations which have all worked:
>myShell ps > fich
>myShell ls -l | wc -l
But not this one:
>myShell ls -l | wc -l >file
here are the two cases specifically developped. I think that the issue is in the case 5 and not in the case 4 because the first command I tried worked (which I shew you above).
case 4: // SYMBOLE : >
if(output==0){
output=1;
execute=1;
for (l=0;l<10;l++){
eltsoutput[l]=eltsCommande[l];
}
}
break;
case 5: // SYMBOLE : |
//if(tube==0){
/*for (l=0;l<10;l++){
eltstube[l]=eltsCommande[l];
}*/
p2=fork();
if(p2==0){
if(tube==0){
freopen( "fichtmp", "w", stdout );
execvp(eltsCommande[0], eltsCommande);
}
return(0);
}
else{ if(background==0){ // SANS MOD BG ATTENDRE FIN FILS
waitpid(p2, NULL, 0);
}
tube=1;
execute=1;
}
break;
Can you help me finding a way to execute two commands at the same time with | and that allow their result to go to a file?
In my shell, the case one work in the case of a redirection with an instruction ";":
}else if(output==1){
close(1);
int filew = creat(eltsCommande[0], 0644);
execvp(eltsoutput[0], eltsoutput);
Maybe I should use this code to make it work?
Looking at the NetBSD /bin/sh source code, I see the following pipe implementation:
static int
sh_pipe(int fds[2])
{
int nfd;
if (pipe(fds))
return -1;
if (fds[0] < 3) {
nfd = fcntl(fds[0], F_DUPFD, 3);
if (nfd != -1) {
close(fds[0]);
fds[0] = nfd;
}
}
if (fds[1] < 3) {
nfd = fcntl(fds[1], F_DUPFD, 3);
if (nfd != -1) {
close(fds[1]);
fds[1] = nfd;
}
}
return 0;
}
This function is called by evalpipe with 2 file descriptors:
STATIC void
evalpipe(union node *n)
{
struct job *jp;
struct nodelist *lp;
int pipelen;
int prevfd;
int pip[2];
TRACE(("evalpipe(0x%lx) called\n", (long)n));
pipelen = 0;
for (lp = n->npipe.cmdlist ; lp ; lp = lp->next)
pipelen++;
INTOFF;
jp = makejob(n, pipelen);
prevfd = -1;
for (lp = n->npipe.cmdlist ; lp ; lp = lp->next) {
prehash(lp->n);
pip[1] = -1;
if (lp->next) {
if (sh_pipe(pip) < 0) {
if (prevfd >= 0)
close(prevfd);
error("Pipe call failed");
}
}
if (forkshell(jp, lp->n, n->npipe.backgnd ? FORK_BG : FORK_FG) == 0) {
INTON;
if (prevfd > 0) {
close(0);
copyfd(prevfd, 0, 1);
close(prevfd);
}
if (pip[1] >= 0) {
close(pip[0]);
if (pip[1] != 1) {
close(1);
copyfd(pip[1], 1, 1);
close(pip[1]);
}
}
evaltree(lp->n, EV_EXIT);
}
if (prevfd >= 0)
close(prevfd);
prevfd = pip[0];
close(pip[1]);
}
if (n->npipe.backgnd == 0) {
exitstatus = waitforjob(jp);
TRACE(("evalpipe: job done exit status %d\n", exitstatus));
}
INTON;
}
evalpipe is called in a switch statement in evaltree as follows:
case NPIPE:
evalpipe(n);
do_etest = !(flags & EV_TESTED);
break;
... which is called by the infinite loop in evalloop, and percolates up the tree till it gets to the eval function. I hope this helps.
I'm using pipe to send an array of numbers to another process to sort them. So far, I'm able to get the result from another process using fdopen. However, I can't figure out how to send data from the pipe as stdin for another process.
Here is my code:
int main ()
{
int fd[2], i, val;
pid_t child;
char file[10];
FILE *f;
pipe(fd);
child = fork();
if (child == 0)
{
close(fd[1]);
dup2(fd[0], STDIN_FILENO);
close(fd[0]);
execl("sort", "sort", NULL);
}
else
{
close(fd[0]);
printf ("BEFORE\n");
for (i = 100; i < 110; i++)
{
write(fd[1], &i, sizeof (int));
printf ("%d\n", i);
}
close(fd[1]);
wait(NULL);
}
}
By the way, how can the other process get input? scanf?
I think your pipe is set up correctly. The problems may start at execl(). For this call you should specify an absolute path, which is probably /bin/sort if you mean the Unix utility. There is also a version of the call execlp() which searches automatically on the PATH.
The next problem is that sort is text based, more specifically line based, and you're sending binary garbage to its STDIN.
In the parent process you should write formatted text into the pipe.
FILE *wpipe = fdopen(fd[1], "w");
for (i = 100; i < 110; i++) {
fprintf(wpipe, "%d\n", i);
...
}
fclose(wpipe);
A reverse loop from 110 down to 100 may test your sorting a bit better.
SO,
There are many similar questions, however none that I have been able to use. My code snippet is as follows:
for(int j=0; j<N; j++) {
pid_t pid = fork();
if (pid == -1) {
exit(-1); //err
} else if (pid == 0) {//kid
stringstream ss;
ss<<j;
execlp("./sub","sub",ss.str().c_str(),NULL);
exit(0);
} else {
/* parent */
}
}
my executing code in sub(.cpp) is:
int main( int argc, char **argv )
{
cout<<argv[i]<<endl;
exit(0);
}
my output is as such:
[terminal prompt '$'] 4
2
3
etc.
Is there a way I could prevent the prompt from displaying on the exec call? and why is it ONLY displaying on the first exec call, and not on every one?
What you see is the normal prompt of your shell, because the parent process terminates very quickly. It is not the output of the exec call. The forked processes print their output after the parent process has terminated.
You can use waitpid() in the parent process to "wait" until all forked process have terminated.
Am I missing something ?
I want to come out of select by calling write in another thread... It never comes out of select.
Code is tested on OSX snow.
fd_set rio, wio;
int pfd[2];
void test(int sleep_time)
{
sleep(sleep_time);
char buf[] = "1";
write(pfd[1], buf, 1);
}
int main(int argc, char* argv[])
{
char buff[80];
int ended = 0;
pipe(pfd);
FD_ZERO(&rio);
FD_ZERO(&wio);
FD_SET(pfd[1], &wio);
FD_SET(pfd[0], &rio);
pthread_t tid; /* the thread identifier */
pthread_attr_t attr; /* set of thread attributes */
pthread_attr_init(&attr);
pthread_create(tid, NULL, test, 3);
while (!ended)
{
// Check my numbers ... they do not go over 1 ... so 2
if (select(2, &rio, &wio, NULL, 0) < 0)
perror("select");
else
{
if (FD_ISSET(pfd[1], &wio))
{
if ((read(pfd[0], &buff, 80))<0)
perror("read");
ended = 1;
}
}
}
I believe you have 2 errors:
1 - your select call is limiting the check to a max of fd 2, where the pipe will probably have larger FDs since 0, 1, and 2 are already opened for stdin, stdout, stderr. The pipe FDs will presumably have fds 3 and 4 so you actually need to determine the larger of the 2 pipe FDs and use that for the limit in the select instead of 2.
int maxfd = pfd[1];
if( pfd[0] > maxfd ) {
maxfd = pfd[0];
}
...
2 - After select returns, you are looking at the wio and pipe write FD when you need to instead look to see if there is anything available to READ:
if (FD_ISSET(pfd[0], &rio)) {
Under Linux, my C++ application is using fork() and execv() to launch multiple instances of OpenOffice so as to view some powerpoint slide shows. This part works.
Next I want to be able to move the OpenOffice windows to specific locations on the display. I can do that with the XMoveResizeWindow() function but I need to find the Window for each instance.
I have the process ID of each instance, how can I find the X11 Window from that ?
UPDATE - Thanks to Andy's suggestion, I have pulled this off. I'm posting the code here to share it with the Stack Overflow community.
Unfortunately Open Office does not seem to set the _NET_WM_PID property so this doesn't ultimately solve my problem but it does answer the question.
// Attempt to identify a window by name or attribute.
// by Adam Pierce <adam#doctort.org>
#include <X11/Xlib.h>
#include <X11/Xatom.h>
#include <iostream>
#include <list>
using namespace std;
class WindowsMatchingPid
{
public:
WindowsMatchingPid(Display *display, Window wRoot, unsigned long pid)
: _display(display)
, _pid(pid)
{
// Get the PID property atom.
_atomPID = XInternAtom(display, "_NET_WM_PID", True);
if(_atomPID == None)
{
cout << "No such atom" << endl;
return;
}
search(wRoot);
}
const list<Window> &result() const { return _result; }
private:
unsigned long _pid;
Atom _atomPID;
Display *_display;
list<Window> _result;
void search(Window w)
{
// Get the PID for the current Window.
Atom type;
int format;
unsigned long nItems;
unsigned long bytesAfter;
unsigned char *propPID = 0;
if(Success == XGetWindowProperty(_display, w, _atomPID, 0, 1, False, XA_CARDINAL,
&type, &format, &nItems, &bytesAfter, &propPID))
{
if(propPID != 0)
{
// If the PID matches, add this window to the result set.
if(_pid == *((unsigned long *)propPID))
_result.push_back(w);
XFree(propPID);
}
}
// Recurse into child windows.
Window wRoot;
Window wParent;
Window *wChild;
unsigned nChildren;
if(0 != XQueryTree(_display, w, &wRoot, &wParent, &wChild, &nChildren))
{
for(unsigned i = 0; i < nChildren; i++)
search(wChild[i]);
}
}
};
int main(int argc, char **argv)
{
if(argc < 2)
return 1;
int pid = atoi(argv[1]);
cout << "Searching for windows associated with PID " << pid << endl;
// Start with the root window.
Display *display = XOpenDisplay(0);
WindowsMatchingPid match(display, XDefaultRootWindow(display), pid);
// Print the result.
const list<Window> &result = match.result();
for(list<Window>::const_iterator it = result.begin(); it != result.end(); it++)
cout << "Window #" << (unsigned long)(*it) << endl;
return 0;
}
The only way I know to do this is to traverse the tree of windows until you find what you're looking for. Traversing isn't hard (just see what xwininfo -root -tree does by looking at xwininfo.c if you need an example).
But how do you identify the window you are looking for? Some applications set a window property called _NET_WM_PID.
I believe that OpenOffice is one of the applications that sets that property (as do most Gnome apps), so you're in luck.
Check if /proc/PID/environ contains a variable called WINDOWID
Bit late to the party. However:
Back in 2004, Harald Welte posted a code snippet that wraps the XCreateWindow() call via LD_PRELOAD and stores the process id in _NET_WM_PID. This makes sure that each window created has a PID entry.
http://www.mail-archive.com/devel#xfree86.org/msg05806.html
Try installing xdotool, then:
#!/bin/bash
# --any and --name present only as a work-around, see: https://github.com/jordansissel/xdotool/issues/14
ids=$(xdotool search --any --pid "$1" --name "dummy")
I do get a lot of ids. I use this to set a terminal window as urgent when it is done with a long command, with the program seturgent. I just loop through all the ids I get from xdotool and run seturgent on them.
There is no good way. The only real options I see, are:
You could look around in the process's address space to find the connection information and window ID.
You could try to use netstat or lsof or ipcs to map the connections to the Xserver, and then (somehow! you'll need root at least) look at its connection info to find them.
When spawning an instance you can wait until another window is mapped, assume it's the right one, and `move on.
I took the freedom to re-implement the OP's code using some modern C++ features. It maintains the same functionalities but I think that it reads a bit better. Also it does not leak even if the vector insertion happens to throw.
// Attempt to identify a window by name or attribute.
// originally written by Adam Pierce <adam#doctort.org>
// revised by Dario Pellegrini <pellegrini.dario#gmail.com>
#include <X11/Xlib.h>
#include <X11/Xatom.h>
#include <iostream>
#include <vector>
std::vector<Window> pid2windows(pid_t pid, Display* display, Window w) {
struct implementation {
struct FreeWrapRAII {
void * data;
FreeWrapRAII(void * data): data(data) {}
~FreeWrapRAII(){ XFree(data); }
};
std::vector<Window> result;
pid_t pid;
Display* display;
Atom atomPID;
implementation(pid_t pid, Display* display): pid(pid), display(display) {
// Get the PID property atom
atomPID = XInternAtom(display, "_NET_WM_PID", True);
if(atomPID == None) {
throw std::runtime_error("pid2windows: no such atom");
}
}
std::vector<Window> getChildren(Window w) {
Window wRoot;
Window wParent;
Window *wChild;
unsigned nChildren;
std::vector<Window> children;
if(0 != XQueryTree(display, w, &wRoot, &wParent, &wChild, &nChildren)) {
FreeWrapRAII tmp( wChild );
children.insert(children.end(), wChild, wChild+nChildren);
}
return children;
}
void emplaceIfMatches(Window w) {
// Get the PID for the given Window
Atom type;
int format;
unsigned long nItems;
unsigned long bytesAfter;
unsigned char *propPID = 0;
if(Success == XGetWindowProperty(display, w, atomPID, 0, 1, False, XA_CARDINAL,
&type, &format, &nItems, &bytesAfter, &propPID)) {
if(propPID != 0) {
FreeWrapRAII tmp( propPID );
if(pid == *reinterpret_cast<pid_t*>(propPID)) {
result.emplace_back(w);
}
}
}
}
void recurse( Window w) {
emplaceIfMatches(w);
for (auto & child: getChildren(w)) {
recurse(child);
}
}
std::vector<Window> operator()( Window w ) {
result.clear();
recurse(w);
return result;
}
};
//back to pid2windows function
return implementation{pid, display}(w);
}
std::vector<Window> pid2windows(const size_t pid, Display* display) {
return pid2windows(pid, display, XDefaultRootWindow(display));
}
int main(int argc, char **argv) {
if(argc < 2)
return 1;
int pid = atoi(argv[1]);
std::cout << "Searching for windows associated with PID " << pid << std::endl;
// Start with the root window.
Display *display = XOpenDisplay(0);
auto res = pid2windows(pid, display);
// Print the result.
for( auto & w: res) {
std::cout << "Window #" << static_cast<unsigned long>(w) << std::endl;
}
XCloseDisplay(display);
return 0;
}
Are you sure you have the process ID of each instance? My experience with OOo has been that trying to run a second instance of OOo merely converses with the first instance of OOo, and tells that to open the additional file.
I think you're going to need to use the message-sending capabilities of X to ask it nicely for its window. I would hope that OOo documents its coversations somewhere.
If you use python, I found a way here, the idea is from BurntSushi
If you launched the application, then you should know its cmd string, with which you can reduce calls to xprop, you can always loop through all the xids and check if the pid is the same as the pid you want
import subprocess
import re
import struct
import xcffib as xcb
import xcffib.xproto
def get_property_value(property_reply):
assert isinstance(property_reply, xcb.xproto.GetPropertyReply)
if property_reply.format == 8:
if 0 in property_reply.value:
ret = []
s = ''
for o in property_reply.value:
if o == 0:
ret.append(s)
s = ''
else:
s += chr(o)
else:
ret = str(property_reply.value.buf())
return ret
elif property_reply.format in (16, 32):
return list(struct.unpack('I' * property_reply.value_len,
property_reply.value.buf()))
return None
def getProperty(connection, ident, propertyName):
propertyType = eval(' xcb.xproto.Atom.%s' % propertyName)
try:
return connection.core.GetProperty(False, ident, propertyType,
xcb.xproto.GetPropertyType.Any,
0, 2 ** 32 - 1)
except:
return None
c = xcb.connect()
root = c.get_setup().roots[0].root
_NET_CLIENT_LIST = c.core.InternAtom(True, len('_NET_CLIENT_LIST'),
'_NET_CLIENT_LIST').reply().atom
raw_clientlist = c.core.GetProperty(False, root, _NET_CLIENT_LIST,
xcb.xproto.GetPropertyType.Any,
0, 2 ** 32 - 1).reply()
clientlist = get_property_value(raw_clientlist)
cookies = {}
for ident in clientlist:
wm_command = getProperty(c, ident, 'WM_COMMAND')
cookies[ident] = (wm_command)
xids=[]
for ident in cookies:
cmd = get_property_value(cookies[ident].reply())
if cmd and spref in cmd:
xids.append(ident)
for xid in xids:
pid = subprocess.check_output('xprop -id %s _NET_WM_PID' % xid, shell=True)
pid = re.search('(?<=\s=\s)\d+', pid).group()
if int(pid) == self.pid:
print 'found pid:', pid
break
print 'your xid:', xid