Develop Reference

Bash script in C language for android ndk

I have a problem with this:
C code
#define CREATE_HTML_FILE_SCRIPT "/bin/curl https://coinmarketcap.com/it/currencies/bytecoin-bcn/ > /data/data/com.example.bytecoin/bcn.html"
#define CREATE_TEMP_FILE_SCRIPT "/data/local/lynx /data/data/com.example.bytecoin/bcn.html -dump > /data/data/com.example.bytecoin/bcn.txt"
system(CREATE_HTML_FILE_SCRIPT);
system(CREATE_TEMP_FILE_SCRIPT);
If I run from adb shell these commands all works well but when these command are executed from the app, file.html and file.txt are empty... I don't understand why and how I can solve it.

Well, lynx is an interactive program, so I think you'll run in trouble when using it from a system() call. But not with curl:
/* pru_curl-1.c */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
char *cmd = "curl https://www.google.com/";
system(cmd); /* you will get the output of curl on stdout */
exit(EXIT_SUCCESS);
}
This is with curl redirecting its output in the shell call with the > operator:
/* pru_curl-2.c */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
char *cmd = "curl https://www.google.com/ >output_file-2";
/* you will get the output of curl on output_file-2 */
system(cmd);
exit(EXIT_SUCCESS);
}
Curl, on the other side, allows you to specify -o output_file.txt and you'll be able to read the file, once the program has finished.
/* pru_curl-3.c */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
char *cmd = "curl https://www.google.com/ -o output_file-3";
/* you will get the output of curl on output_file-3 */
system(cmd);
exit(EXIT_SUCCESS);
}
You have a third alternative, which is using popen(3), that allows you to start the program as a subcommand, and read the output of that program from the FILE * descriptor you get from popen(3). You could use it like this (processing character by character):
/* pru_curl-4.c */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
char *cmd = "curl https://www.google.com/";
FILE *f = popen(cmd, "r");
if (!f) {
fprintf(stderr, "%s: %s\n",
cmd, strerror(errno));
exit(EXIT_FAILURE);
}
int c;
while((c = fgetc(f)) != EOF) {
printf("[%d]", c); /* you will get the downloaded file as
* sequences of numbers (the character
* values) embedded in square brackets on
* stdout */
}
pclose(f);
exit(EXIT_SUCCESS);
}
or (processing line by line):
/* pru_curl-5.c */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
char *cmd = "curl https://www.google.com/";
FILE *f = popen(cmd, "r");
if (!f) {
fprintf(stderr, "%s: %s\n",
cmd, strerror(errno));
exit(EXIT_FAILURE);
}
char line[256];
while (fgets(line, sizeof line, f)) {
/* you'll get your output in chunks of one line, or 256 bytes
* ---if longer---, encapsulated by a pair of square brackets
* drawn in a different color (gren, by the escape sequences
* used) */
fprintf(stderr,
"\033[1;33m[\033[m%s\033[32m]\033[m",
line);
}
pclose(f);
exit(EXIT_SUCCESS);
}
or (by blocks):
/* pru_curl-6.c */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define N 8 /* blocks in buffer */
#define CPB 11 /* chars per block */
int main()
{
char *cmd = "curl https://www.google.com/";
FILE *f = popen(cmd, "r");
if (!f) {
fprintf(stderr, "%s: %s\n",
cmd, strerror(errno));
exit(EXIT_FAILURE);
}
char block[N][CPB];
int n;
char *sep = "";
do {
/* print a blanck line between groups */
printf("%s", sep);
sep = "\n";
/* we read as many CPB byte blocks as possible to fill the
* N registers in buffer.
* Then we start again until we don't fill completely the
* buffer. */
n = fread(block, sizeof block[0], N, f);
int i;
for (i = 0; i < n; i++) {
printf("[%.*s]\n", (int)sizeof block[i], block[i]);
}
printf("finished one loop of %d blocks of %d chars, each.\n",
N, (int) sizeof block[0]);
} while (n == N);
/* n < N, so we are finished, check that probably the last register is
* not printed because it was not complete. */
pclose(f);
exit(EXIT_SUCCESS);
}
(All these examples are complete and have been tested before posting)
Edit
I have completed the code for the six programs and now all of them are executables with just building with:
$ cc pru_curl-<i>.c -o pru_curl-<i> # <i> is the program number
$ _
In each case, you can execute the program by just running:
$ pru_curl-<i>
.... <-- a lot of output (or to a file) about the contents of the root page of google.
$ _

Android kernel build error: core_ctl.c - dereferencing pointer to incomplete type

This kernel builds fine with the ARM GCC toolchain.. for some reason, the aarch64 toolchain throws this error.
kernel/sched/core_ctl.c: In function 'cpufreq_gov_cb':
kernel/sched/core_ctl.c:1086:25: error: dereferencing pointer to incomplete type
core_ctl_set_busy(info->cpu, info->load);
^
kernel/sched/core_ctl.c:1086:36: error: dereferencing pointer to incomplete type
core_ctl_set_busy(info->cpu, info->load);
^
scripts/Makefile.build:257: recipe for target 'kernel/sched/core_ctl.o' failed
Here's the struct at the very beginning of the file where "cpu" is defined (can't find load in the c file):
#include <linux/init.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/cpufreq.h>
#include <linux/timer.h>
#include <linux/kthread.h>
#include <linux/sched.h>
#include <linux/sched/rt.h>
#include <linux/mutex.h>
#include <trace/events/sched.h>
#define MAX_CPUS_PER_GROUP 4
struct cpu_data {
/* Per CPU data. */
bool inited;
bool online;
bool rejected;
bool is_busy;
bool not_preferred;
unsigned int busy;
unsigned int cpu;
struct list_head sib;
unsigned int first_cpu;
struct list_head pending_sib;
/* Per cluster data set only on first CPU */
unsigned int min_cpus;
unsigned int max_cpus;
unsigned int offline_delay_ms;
unsigned int busy_up_thres[MAX_CPUS_PER_GROUP];
unsigned int busy_down_thres[MAX_CPUS_PER_GROUP];
unsigned int online_cpus;
unsigned int avail_cpus;
unsigned int num_cpus;
unsigned int need_cpus;
unsigned int task_thres;
s64 need_ts;
struct list_head lru;
bool pending;
spinlock_t pending_lock;
bool is_big_cluster;
int nrrun;
bool nrrun_changed;
struct timer_list timer;
struct task_struct *hotplug_thread;
struct kobject kobj;
struct list_head pending_lru;
bool disabled;
};
What could make the compiler report incomplete type? I'm not too familiar with pointers and structures in C yet.. can't figure it out.

It seems that the header file for struct cpufreq_govinfo is missing when the kernel/sched/core_ctl.c is compiled on your machine.
struct cpufreq_govinfo {
unsigned int cpu;
unsigned int load;
unsigned int sampling_rate_us;
};
On my machine(ARM:CortexA7), the GCC compiler does not throw compile error since the following head file is properly included.
kernel/include/linux/cpufreq.h
In addition, the following patch will enable you to have preprocessed file after building Linux Kernel.
diff --git a/Makefile b/Makefile
index b03ca98..f52240c 100644
--- a/Makefile
+++ b/Makefile
## -406,6 +406,7 ## KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
-fno-strict-aliasing -fno-common \
-Werror-implicit-function-declaration \
-Wno-format-security \
+ -save-temps=obj \
-std=gnu89
If you take a look at the preprocessed file .tmp_core_ctl.i, you would be able to see all of the header files for compiling core_ctl.c

__android_log_print equivalent for printf

I am trying to port this logging statement to work, so it will run on linux and android my #define'ing it:
__android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
I have cross-compiled my app to run on both Linux and Android. However, as linux doesn't have the equivalent I have tried to do my own.
/** ANDROID */
#if defined(__ANDROID__)
#include <android/log.h>
#define LOG_ERROR ANDROID_LOG_ERROR
#define LOG(PRIORITY, fmt, ...) __android_log_print(ANDROID_LOG_UNKNOWN, LOG_TAG, fmt, ##__VA_ARGS__)
/** LINUX */
#elif defined(linux) || defined(__linux) || defined(__linux__)
#define LOG_ERROR LINUX_LOG_ERROR
#define LOG(PRIORITY, fmt, ...) printf(PRIORITY fmt, ##__VA_ARGS__)
#endif
And then using it like this when running under linux
LOG(LOG_ERROR, "Testing loggging [ %d ]", test);
Is there a better way to do this?
Many thanks for any suggestions,

I managed to solve it this way. Here is the complete solution.
This would be in a header file
typedef enum levels_tag levels_e;
enum levels_tag {
LOG_UNKNOWN = 0,
LOG_DEFAULT,
LOG_VERBOSE,
LOG_DEBUG,
LOG_INFO,
LOG_WARN,
LOG_ERROR,
LOG_FATAL,
LOG_SILENT,
LOG_LAST
};
/* ANDRIOD IMPLEMENTATION */
#if defined( __ARM_EABI__)
#include <android/log.h>
levels_e levels[LOG_LAST] = {LOG_UNKNOWN,
LOG_DEFAULT,
LOG_VERBOSE,
LOG_DEBUG,
LOG_INFO,
LOG_WARN,
LOG_ERROR,
LOG_FATAL,
LOG_SILENT};
#define LOG_TAG "MODULE_LOG_SIP"
#define LOGGING(PRIORITY, fmt, ...) __android_log_print(levels[PRIORITY], LOG_TAG, fmt, ##__VA_ARGS__)
/* LINUX IMPLEMENTATION */
#elif defined(linux) || defined(__linux) || defined(__linux__)
char *priority_levels[] = {"UNKNOWN",
"DEFAULT",
"VERBOSE",
"DEBUG",
"INFO",
"WARN",
"ERROR",
"FATAL",
"SILENT",
NULL };
#define LOGGING(PRIORITY, fmt, ...) \
do { \
char *priority = priority_levels[PRIORITY]; \
printf("%s/%s:%d [%s] " fmt " \n", __FILE__, __func__, __LINE__, priority, ##__VA_ARGS__); \
} while(0)
#endif
#define LOG(PRIORITY, fmt, ...) LOGGING(PRIORITY, fmt, ##__VA_ARGS__)
And in your source files you would just call the LOG macro like this:
LOG(LOG_FATAL, "Failed to create and initialize application instance [ %d ]", errno);
Now if you were to compile on linux it would use the printf statement. And if you were to compile on Android it would use the __android_log_print statement. Both would produce the same formatted output.
Hope this helps someone else.

You can also use family of syslog() functions to make output to system log instead of stdout/stderr (see syslog.h):
void openlog(const char *ident, int option, int facility);
void syslog(int priority, const char *format, ...);
void closelog(void);
Logs can be viewed in /var/log (file depends on options of syslog, by default in many systems logs are in the file "messages"). Sometimes this way is a better than stdout/stderr, but you have to use openlog/closelog. Unfortunately, syslog's priorities are different comparing to android priorities and thus it doesn't allow simple macro definition with transparent priorities.Syslog priorities:
#define LOG_EMERG 0 /* system is unusable */
#define LOG_ALERT 1 /* action must be taken immediately */
#define LOG_CRIT 2 /* critical conditions */
#define LOG_ERR 3 /* error conditions */
#define LOG_WARNING 4 /* warning conditions */
#define LOG_NOTICE 5 /* normal but significant condition */
#define LOG_INFO 6 /* informational */
#define LOG_DEBUG 7 /* debug-level messages */
Priorities of android log:
/*
* Android log priority values, in ascending priority order.
*/
typedef enum android_LogPriority {
ANDROID_LOG_UNKNOWN = 0,
ANDROID_LOG_DEFAULT, /* only for SetMinPriority() */
ANDROID_LOG_VERBOSE,
ANDROID_LOG_DEBUG,
ANDROID_LOG_INFO,
ANDROID_LOG_WARN,
ANDROID_LOG_ERROR,
ANDROID_LOG_FATAL,
ANDROID_LOG_SILENT, /* only for SetMinPriority(); must be last */
} android_LogPriority;

pass string from java to c++ and using popen with NDK cased errors?

i am using NDK to join java with C++ this my code :
MainActivity.java
public class MainActivity extends Activity {
/*Don't forget to load the library!!*/
static {
System.loadLibrary("NDK1");
}
public native String exec(String cmd);
Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
# Here we give our module name and source file(s)
LOCAL_MODULE := NDK1
LOCAL_SRC_FILES := NDK1.cpp
include $(BUILD_SHARED_LIBRARY)
Application.mk
APP_ABI := armeabi armeabi-v7a
APP_STL := gnustl_static
NDK1.cpp
#include <string>
#include <iostream>
#include <stdio.h>
#include <jni.h>
std::string exec(char* cmd) {
FILE* pipe = popen(cmd, "r");
if (!pipe) return "ERROR";
char buffer[128];
std::string result = "";
while(!feof(pipe)) {
if(fgets(buffer, 128, pipe) != NULL)
result += buffer;
}
pclose(pipe);
return result;
}
jstring Java_com_example_ndk1_MainActivity_exec(JNIEnv* env, jobject javaThis , jstring cmd) {
char * res;
res = env->GetStringUTFChars(cmd ) ;
std::string result = exec(res);
return env->NewStringUTF(result);
}
but have this error !!!
$ /cygdrive/c/android-ndk-r4/ndk-build
make: Warning: File `/cygdrive/c/android-ndk-r4/build/core/import-locals.mk' has modification time 140680622 s in the future
Compile++ thumb : NDK1 <= NDK1.cpp
jni/NDK1.cpp: In function '_jstring* Java_com_example_ndk1_MainActivity_exec(JNIEnv*, jobject, jstring)':
jni/NDK1.cpp:22:39: error: no matching function for call to '_JNIEnv::GetStringUTFChars(_jstring*&)'
jni/NDK1.cpp:22:39: note: candidate is:
C:/android-ndk-r4/platforms/android-14/arch-arm/usr/include/jni.h:860:17: note: char const* _JNIEnv::GetStringUTFChars(jstring, jboolean*)
C:/android-ndk-r4/platforms/android-14/arch-arm/usr/include/jni.h:860:17: note: candidate expects 2 arguments, 1 provided
jni/NDK1.cpp:25:36: error: no matching function for call to '_JNIEnv::NewStringUTF(std::string&)'
jni/NDK1.cpp:25:36: note: candidate is:
C:/android-ndk-r4/platforms/android-14/arch-arm/usr/include/jni.h:854:13: note: _jstring* _JNIEnv::NewStringUTF(char const*)
C:/android-ndk-r4/platforms/android-14/arch-arm/usr/include/jni.h:854:13: note: no known conversion for argument 1 from 'std::string {aka std::basic_string<char>}' to 'char const*'
/cygdrive/c/android-ndk-r4/build/core/build-binary.mk:269: recipe for target `obj/local/armeabi/objs/NDK1/NDK1.o' failed
make: *** [obj/local/armeabi/objs/NDK1/NDK1.o] Error 1

after many tries to catch the problem this is the solution without causing any error :
jstring Java_com_example_ndk1_MainActivity_exec(JNIEnv* env, jobject javaThis , jstring cmd) {
const char * res;
jboolean isCopy;
res = env->GetStringUTFChars(cmd, &isCopy);
if (isCopy == JNI_TRUE) {
(env)->ReleaseStringUTFChars(cmd, res);
}
std::string result = exec(res);
return (env)->NewStringUTF((const char* )result.c_str());
}

[edited to make the answer more generic - there are several errors in the code]
For every error of the type no matching function for call to, look up the definition of the function in the JNI reference
Make sure that you are:
Passing all required parameters
The parameters are of the required type
For example, the call to GetStringUTFChars is missing parameters and the call to NewStringUTF doesn't take a std::string as parameter. It wants a const char *.
For the NewStringUTF, try:
return (*env)->NewStringUTF(env, (const char*)result.c_str());
This JNI tutorial is also nice: http://www.steveolyo.com/JNI/JNI.html

Android NDK: Function va_start / va_end could not be resolved

I trying to use va_start and va_end functions in my project, but eclipse don't want to resolve it as functions. gcc compiles whole project without errors...
[myfile.cpp]
#include <stdio.h>
#include <stdarg.h>
[...]
inline void ShowDbgMsg( const char* str, ... )
{
va_list argptr;
va_start(argptr, str);
vprintf(str, argptr);
va_end(argptr);
}
[...]
[Android.mk]
[...]
LOCAL_C_INCLUDES := jni/pvrTools/ jni/igel/ $(STLPORT_BASE)/stlport
[...]
Eclipse says:
[...]
Description Resource Path Location Type
Function 'va_start' could not be resolved igel.comdef.h /NativeProject/jni/igel line 195 Semantic Error
Function 'va_end' could not be resolved igel.comdef.h /NativeProject/jni/igel line 203 Semantic Error
Function 'va_start' could not be resolved igel.string.h /NativeProject/jni/igel line 341 Semantic Error
Function 'va_end' could not be resolved igel.string.h /NativeProject/jni/igel line 351 Semantic Error
[...]
So, it looks like Eclipse unable to locate something... How to solve this issue?
Thanks in advance!
P.S.> Project->Index->Rebuild didn't help. :(

My solution is also not pretty. But after you've deleted the error markers 100 times, try putting this code somewhere before you include stdlib.h. Then define ECLIPSEBUILD=1 in Project::Properties::C++ General::Paths and Symbols.
#if ECLIPSEBUILD // this part is just to fix spurious Eclipse errors
typedef __builtin_va_list va_list;
#define va_start(v,l) __builtin_va_start(v,l)
#define va_end(v) __builtin_va_end(v)
#define va_arg(v,l) __builtin_va_arg(v,l)
#if !defined(__STRICT_ANSI__) || __STDC_VERSION__ + 0 >= 199900L || defined(__GXX_EXPERIMENTAL_CXX0X__)
#define va_copy(d,s) __builtin_va_copy(d,s)
#endif
#define __va_copy(d,s) __builtin_va_copy(d,s)
typedef __builtin_va_list __gnuc_va_list;
typedef __gnuc_va_list va_list;
typedef va_list __va_list;
#endif

I solve this issue by replacing my va_* code with embedded compiler features:
#ifdef IGEL_PLATFORM_ANDROID
# define ShowDbgMsg(...) ((void)__android_log_print(ANDROID_LOG_INFO, "igel-debug", __VA_ARGS__))
#else
inline void ShowDbgMsg( const char* str, ... )
{
va_list argptr;
va_start(argptr, str);
vprintf(str, argptr);
va_end(argptr);
}
#endif // IGEL_PLATFORM_ANDROID
I know it's not a good solution, but it works.

#include <stdarg.h> // includes va_list
inline void ShowDbgMsg(char* format, ...)
{
va_list ap;
va_start( ap, format );
// replace vfprintf( stderr, format, ap ) with:
__android_log_vprint(0, __FILE__, format, ap);
va_end( ap );
}