Программирование linux

Linux

man !

$ man hello
HELLO(1) User Commands HELLO(1)

NAME
hello - friendly greeting program

SYNOPSIS
hello [OPTION]...

DESCRIPTION
Print a friendly, customizable greeting.

-h, --help
display this help and exit

-v, --version
display version information and exit

-t, --traditional
use traditional greeting format

-n, --next-generation
use next-generation greeting format

-g, --greeting=TEXT
use TEXT as the greeting message

GCC = + + +

cppcc1, cc1plus, ...ascollect2

$ cat hello.c

#include

int main()
{
printf("Hello World\n");
}

$ gcc -o hello hello.c

$ ./hello

Hello World

$ cat hello.c

#include

int main()
{
printf("Hello World\n")
}

$ gcc -o hello hello.c

hello.c: In function 'main': hello.c:7: error: syntax error before '}' token

$ cat main.c

int main()
{
print_hello();
}

$ cat hello.c

#include

void print_hello()
{
}

$ gcc -c main.c

$ gcc -c hello.c

$ ls
hello.c hello.o main.c main.o

$ gcc -o hello main.o hello.o

$ ls hello*
hello.c hello.o main.c main.o

$ ./hello

Hello World

$ gcc -o hello hello.c main.c -Wall

main.c: In function main:
main.c:1:1: warning: implicit declaration of function print_hello
main.c:1:1: warning: control reaches end of non-void function

$ nm hello.o

00000000 T print_hello
U puts

$ ldd hello

linux-vdso.so.1 => (0x00110000)
libc.so.6 => /lib/libc.so.6 (0x00a57000)
/lib/ld-linux.so.2 (0x00a38000)

$ cat Makefile

hello: main.o hello.o
gcc -o hello main.o hello.o

main.o: main.c
gcc -c main.c

hello.o: hello.c
gcc -c hello.c

clean:
rm -f *.o hello

http://habrahabr.ru/blogs/development/111691

$ make

gcc -c main.c
gcc -c hello.c
gcc -o hello main.o hello.o

$ ls
hello hello.c hello.o main.c main.o Makefile

void openlog(char *ident, int option,
int facility);

void syslog(int priority, char *format, );

void closelog();

#include

int main()
{
int i;

openlog("test", LOG_PID, LOG_USER);

syslog(LOG_DEBUG,"try to sending 5 messages");

for (i = 0; i < 5; ++i)
syslog(LOG_INFO,"info message [i = %i]",i);

closelog();
};

$ tail /var/log/debug

Dec 20 11:25:04 linux test[6222]: try to sending 5 messages

$ tail /var/log/messages

Dec 20 11:25:04 linux test[6222]: info message [i = 0]

$ cat hello.h

void h_world();
void g_world();

$ cat hello.c

#include
#include "hello.h"

void h_world()
{
}

void g_world()
{
printf ("Goodbye World\n");
}

$ cat main.c

#include "hello.h"

int main()
{
h_world();
g_world();
}

$ gcc -c main.c

$ gcc -c hello.c

$ ar cr libhello.a hello.o

$ gcc -o hello main.o -L. -lhello

$ ar t libhello.a
hello.o

$ ar x libhello.a hello.o

$ gcc -c -fPIC -o hello.o hello.c

$ gcc -shared -o libhello.so hello.o

$ gcc -o hello -L. -lhello main.c

$ ./hello
./hello: error while loading shared libraries: libhello.so: cannot open shared object file: No such file or directory

$ ldd hello
...
libhello.so => not found
...

$ gcc -o hello -L. -lhello -Wl,-rpath,. main.o

$ ./hello

Hello World
Goodbye World

$ ldd hello
libhello.so => ./libhello.so (0x00a57000)

$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$PWD

void *dlopen(char const *filename, int flag);

void *dlsym(void *handle, char *symbol);

dlclose(void *handle);

-dl

#include

double pow(double x, double y);

int main()
{
void *library;
double (*power)(double, double);

library = dlopen("/lib/libmath.so",RTLD_LAZY);

if (!library)
return dlerror();

power = dlsym(library, pow);

dlclose(library);
};

USER -
HOME -
PATH - , , ""
PWD -
OLDPWD -
SHELL -
HOSTNAME -
QTDIR - QT
LD_LIBRARY_PATH - ""
LANG -
DISPLAY - X11

extern char ** environ; //declared in unistd.h

char *getenv(char const *name);

int setenv(char const *name, char const *value, int overwrite);

int unsetenv(char const *name);

-

int open(char const* filename, int flags);

int close(int fd);

ssize_t read(int fd, void *buffer, size_t count);

ssize_t write(int fd, const void * buffer, size_t count);

off_t lseek(int fd, ott_t offset, int against);

#include
#include
#include // read(), write(), close() #include // open(), O_RDONLY
#include //S_IRUSR
#include // mode_t

#define BUFFER_SIZE64

int main(int argc, char ** argv)
{
int fd;
ssize_t read_bytes;
ssize_t written_bytes;
char buffer[BUFFER_SIZE];

if (argc < 2)
{
fprintf(stderr, "Too few arguments\n");
exit (1);
}

fd = open(argv[1], O_RDONLY);

if (fd < 0)
{
fprintf(stderr, "Cannot open file\n");
exit (1);
}

while ((read_bytes = read(fd, buffer, BUFFER_SIZE)) > 0)
{
written_bytes = write(FILENO(stdout), buffer, read_bytes);

if (written_bytes != read_bytes)
{
fprintf (stderr, "Cannot write\n");
exit (1);
}
}

if (read_bytes < 0)
{
fprintf(stderr, "myread: Cannot read file\n");
exit (1);
}

close (fd);

return 0;
}

pid_t getpid(); //PID

pid_t getppid(); //PID

pid_t fork(); //

int execve(char const *path, char * const argv[], char *const envp[]); //

#include
#include

int main()
{
char *echo_args[] = { "echo", "child", NULL};

if (fork())
printf("parent");
else
execve("/bin/echo", echo_args, environ);

return 0;
}

IPC

int pipe(int pipefd[2]); //

int mkfifo(char const *pathname,
mode_t mode); //

#include
#include
#include

int main (int argc, char * argv[])
{
int pipedes[2];
pid_t pid;

pipe(pipedes);
pid = fork();

if (pid > 0)
{
char *str = "String passed via pipe\n";

close(pipedes[0]);
write(pipedes[1], (void *)str, strlen(str) + 1);
close(pipedes[1]);
}

else
{
char buf[1024];
int len;

close(pipedes[1]);

while ((len = read(pipedes[0], buf, 1024)) != 0)
write(2, buf, len);

close(pipedes[0]);
}

return 0;
}

int socket(int domain, int type, int protocol);

int connect(int sockfd,
const struct sockaddr *addr,
socklen_t addrlen);

int bind(int sockfd, const struct sockaddr *addr,
socklen_t addrlen);

int listen(int sockfd, int backlog);

int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);

struct hostent *gethostbyname(char const *name);

sock = socket(AF_INET, SOCK_STREAM, 0);

serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(port);

bind(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr);

listen(sock, 1);

new_sock = accept(sock,
(struct sockaddr *)&new_addr,
&new_len);

server = gethostbyname(hostname);

serv_addr.sin_family = AF_INET;
memcpy(&serv_addr.sin_addr.s_addr,
server->h_addr, server->h_length);
serv_addr.sin_port = htons(port);

connect(sock, &serv_addr, sizeof(serv_addr);

#include

void handler(int i)
{
printf("Terminating\n");
exit(EXIT_FAILURE);
}

int main(int argc, char *argv[])
{
signal(SIGSEGV, handler);
kill(getpid(), SIGSEGV);
}

SIGINT ,
SIGKILL ,
SIGTERM
SIGSEGV
SIGCHLD
SIGSTOP
SIGCONT
SIGUSR1

int pthread_create(pthread_t *thread,
pthread_attr_t const *attr,
void *(*start_routine) (void *),
void *arg);

int pthread_join(pthread_t thread, void **retval);

void pthread_exit(void *retval);

int pthread_cancel(pthread_t thread);

-pthread

#include
#include

void *thread(void *arg)
{
printf("Thread %i is running\n", *(int *)arg);
}

int main(int argc, char * argv[])
{
int id1 = 1, id2 = 2;
pthread_t thread1, thread2;

pthread_create(&thread1, NULL, thread, &id1);
pthread_create(&thread2, NULL, thread, &id2);

pthread_join(thread1, NULL);
pthread_join(thread2, NULL);

return errno;
}

pthread_mutex_t
pthread_mutex_lock(mutex)
pthread_mutex_trylock(mutex)
pthread_mutex_unlock(mutex)

pthread_cond_t
pthread_cond_wait(condition, mutex)
pthread_cond_signal(condition)
pthread_cond_broadcast(condition)

pthread_rwlock_t

pthread_barrier_t

IDE

QtCreator
Code::Blocks
Eclipse
Vim
Emacs
NetBeans
MonoDevelop
...

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Программирование linux

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