I need the GNU Linux Code of the function
error_t argp_parse(const struct argp *__restrict __argp,int,char **__restrict,unsigned __flags,int * __arg_index,void *__restrict input)
If someone know where to get or have it ,please send it to me.
Thanks very much !!
Part of glibc, so easily found following the links at gnu.org:
From http://sourceware.org/git/?p=glibc.git;a=blob_plain;f=argp/argp-parse.c;hb=e07bb02a4f9e7d98f79f428a661c5b982286869d:
/* Parse the options strings in ARGC & ARGV according to the argp in ARGP.
FLAGS is one of the ARGP_ flags above. If END_INDEX is non-NULL, the
index in ARGV of the first unparsed option is returned in it. If an
unknown option is present, EINVAL is returned; if some parser routine
returned a non-zero value, it is returned; otherwise 0 is returned. */
error_t
__argp_parse (const struct argp *argp, int argc, char **argv, unsigned flags,
int *end_index, void *input)
{
error_t err;
struct parser parser;
…
Related
I want to use parameters in a program I made in C/C++ languages. Example:
MaxPayne2.exe -developer -developerkeys
I want to use a parameter like this in my exe file. How can I do it?
https://en.cppreference.com/w/cpp/language/main_function
While I would usually recommend adding more context this is your answer.
The standard c++ main has two additional parameters,
int main (int argc, char *argv[]) { }
To use these "arguments" (as they are called) you just reference their point in the argv array.
argc = the number of additional arguments supplied.
argv = the array of argument values supplied.
Example:
int main (int argc, char *argv[])
{
cout << argv[argc-1]; //Prints out the last argument supplied.
}
(note)If my syntax is wrong someone please correct me, my c++ is a bit rusty.
We can get the arguments passed to a process using command "cat /proc/pid/cmdline".
But how to get this progrmmatically.
Open the /proc file:
int fd = open("/proc/$pid/cmdline", O_RDONLY);
and read from it. (The arguments are delimited by '\0'.)
The point of exposing this info in the filesystem is so that you don't need special functions for obtaining it.
Command line arguments are passed to main() as a character array.
Try this simple program:
int main(int argc, const char *argv[])
{
int i;
for(i=0;i<argc;i++)
{
printf("%s\n",argv[i]);
}
return 0;
}
So I've been trying to access command line arguments with indices larger than argc in C++ (because why not) and discovered that there are actually some parameters passed on to the program. The following code produces the following result in my Ubuntu 14.04:
#include <cstdio>
int main (int argc, char** argv) {
for (int i=argc+1; argv[i]!=0; i++)
printf("%3d %s\n", i, argv[i]);
}
This is the output:
2 XDG_VTNR=7
3 LC_PAPER=tr_TR.UTF-8
4 LC_ADDRESS=tr_TR.UTF-8
5 XDG_SESSION_ID=c2
6 XDG_GREETER_DATA_DIR=/var/lib/lightdm-data/kubuzetto
7 SELINUX_INIT=YES
8 LC_MONETARY=tr_TR.UTF-8
9 CLUTTER_IM_MODULE=xim
(and so on)
What is this and is it distro-dependent?
Don't run past argc, it's not defined.
In this case, we know what happened. You see, main() is declared and called as
extern int main(int argc, char **argv, char **envp);
and it just so happens that the the way argv and envp are built leaves envp right after argv, so running off the end encounters envp.
It might change someday, so don't depend on this working. If you wanna depend on the kernel's passing method, provide the kernel's entry point yourself (which must be done in asm [or possibly a naked function] as it doesn't look like a function call).
I need to pass 1 value between programs. In my case, I run (VERY SIMPLE) program within another by calling system("SimpleProgram").
Is there a way how to pass 1 value (integer) returned by SimpleProgram. Neither "return 123" nor "exit(123)" doesnt work.
Is there any elegant way to pass such value? (I dont want to write and read an external file)
EDIT:
The language is C++, the programming is done on BeagleBone with Angstrom distribution.
retCode = system("cd /home/martin/uart/temp/xml_parser && ./xmldom");
Note what the man page for system(3) says about the return code:
The value returned is -1 on error (e.g. fork(2) failed), and the
return status of the command otherwise.
This latter return status is in the format specified in wait(2). Thus, the exit code of the command will
be WEXITSTATUS(status).
So you're almost there. If you have a simple program that returns 123, as you stated:
int main(int argc, char **argv) {
return 123;
}
then you can run it with system(3) and see its return code by using WEXITSTATUS():
#include <iostream>
using namespace std;
#include <stdlib.h>
int main(int argc, char **argv) {
int rc = system(argv[1]);
cout << WEXITSTATUS(rc) << '\n';
}
Naming the first program return123 and the second system:
$ ./system ./return123
123
If you leave off the WEXITSTATUS() and just print rc directly, you will get an incorrect value.
The standard way to do this is with UNIX pipes.
If it's just a hack, you might as well just use the binary return value, but in either case, you'd have to use execve() instead of system().
I want to extract all argv from an existing struct linux_binprm. On kernel 3.4, I tried this piece of code: http://www.mail-archive.com/kernelnewbies#nl.linux.org/msg00278.html in do_excve_common, but it doesn't work. It returns (null). What is the problem and how can I get ALL the arguments in a char * string?
. If you want to get the full command line before the binary loader executing in do_execve_common(), you can try following:
there is one argument *argv in the function do_execve_common() parameter table, why bother to get the argv from "struct linux_binprm"? You can use the *argv directly with following codes. In the do_execve_common(), insert some codes as following:
argc = count(argv, MAX_ARG_STRINGS);
i = 0;
while (i < argc)
{
const char __user *str;
int len;
ret = -EFAULT;
str = get_user_arg_ptr(argv, i);
if (IS_ERR(str))
goto out;
len = strnlen_user(str, MAX_ARG_STRLEN);
if (!len)
goto out;
//copy the str to kernel temporary storage
//NOTE: tmp[] is a string array,
// the memory should have been allocated already for strings storage,
// each string is ended with \0
memcpy(tmp[i], str, len)
}
After executing these codes, I think the argv strings will be all saved in tmp[] array.
. While if you want to get the full command line after binary loader executing, I think at this time the argument page has been setup correctly, then you can try following approach to get the full command line:
There is a function proc_pid_cmdline() in ./fs/proc/base.c file, you can re-use most codes in proc_pid_cmdline() function to get the full command line from the argument page.