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Merge pull request #13668 from wxy/勘误

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PRF:代码错误
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Xingyu.Wang 2019-05-14 09:01:08 +08:00 committed by GitHub
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3 changed files with 88 additions and 92 deletions
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4
published/20181212 TLP - An Advanced Power Management Tool That Improve Battery Life On Linux Laptop.md
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@ -108,7 +108,9 @@ $ sudo apt-get install smartmontools
当基于 Ubuntu 的系统的官方软件包过时时，请使用以下 PPA 存储库，该存储库提供最新版本。运行以下命令以使用 PPA 安装 TLP。
```
$ sudo apt-get install tlp tlp-rdw
$ sudo add-apt-repository ppa:linrunner/tlp
$ sudo apt-get update
$ sudo apt-get install tlp
```
对于基于 Arch Linux 的系统，使用 [Pacman 命令][9] 安装 TLP。

95
published/20190415 Inter-process communication in Linux- Shared storage.md
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@ -62,47 +62,42 @@ producer-------->| disk file |<-------consumer
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#define FileName "data.dat"
#define DataString "Now is the winter of our discontent\nMade glorious summer by this sun of York\n"
void report_and_exit(const char* msg) {
[perror][4](msg);
[exit][5](-1); /* EXIT_FAILURE */
perror(msg);
exit(-1); /* EXIT_FAILURE */
}
int main() {
struct flock lock;
lock.l_type = F_WRLCK; /* read/write (exclusive) lock */
lock.l_type = F_WRLCK; /* read/write (exclusive versus shared) lock */
lock.l_whence = SEEK_SET; /* base for seek offsets */
lock.l_start = 0; /* 1st byte in file */
lock.l_len = 0; /* 0 here means 'until EOF' */
lock.l_pid = getpid(); /* process id */
int fd; /* file descriptor to identify a file within a process */
if ((fd = open(FileName, O_RDONLY)) < 0) /* -1 signals an error */
report_and_exit("open to read failed...");
if ((fd = open(FileName, O_RDWR | O_CREAT, 0666)) < 0) /* -1 signals an error */
report_and_exit("open failed...");
/* If the file is write-locked, we can't continue. */
fcntl(fd, F_GETLK, &lock); /* sets lock.l_type to F_UNLCK if no write lock */
if (lock.l_type != F_UNLCK)
report_and_exit("file is still write locked...");
if (fcntl(fd, F_SETLK, &lock) < 0) /** F_SETLK doesn't block, F_SETLKW does **/
report_and_exit("fcntl failed to get lock...");
else {
write(fd, DataString, strlen(DataString)); /* populate data file */
fprintf(stderr, "Process %d has written to data file...\n", lock.l_pid);
}
lock.l_type = F_RDLCK; /* prevents any writing during the reading */
if (fcntl(fd, F_SETLK, &lock) < 0)
report_and_exit("can't get a read-only lock...");
/* Read the bytes (they happen to be ASCII codes) one at a time. */
int c; /* buffer for read bytes */
while (read(fd, &c, 1) > 0) /* 0 signals EOF */
write(STDOUT_FILENO, &c, 1); /* write one byte to the standard output */
/* Release the lock explicitly. */
/* Now release the lock explicitly. */
lock.l_type = F_UNLCK;
if (fcntl(fd, F_SETLK, &lock) < 0)
report_and_exit("explicit unlocking failed...");
close(fd);
return 0;
close(fd); /* close the file: would unlock if needed */
return 0; /* terminating the process would unlock as well */
}
```
@ -140,8 +135,8 @@ lock.l_type = F_UNLCK;
#define FileName "data.dat"
void report_and_exit(const char* msg) {
[perror][4](msg);
[exit][5](-1); /* EXIT_FAILURE */
perror(msg);
exit(-1); /* EXIT_FAILURE */
}
int main() {
@ -240,37 +235,37 @@ This is the way the world ends...
#include "shmem.h"
void report_and_exit(const char* msg) {
[perror][4](msg);
[exit][5](-1);
perror(msg);
exit(-1);
}
int main() {
int fd = shm_open(BackingFile, /* name from smem.h */
O_RDWR | O_CREAT, /* read/write, create if needed */
AccessPerms); /* access permissions (0644) */
O_RDWR | O_CREAT, /* read/write, create if needed */
AccessPerms); /* access permissions (0644) */
if (fd < 0) report_and_exit("Can't open shared mem segment...");
ftruncate(fd, ByteSize); /* get the bytes */
caddr_t memptr = mmap(NULL, /* let system pick where to put segment */
ByteSize, /* how many bytes */
PROT_READ | PROT_WRITE, /* access protections */
MAP_SHARED, /* mapping visible to other processes */
fd, /* file descriptor */
0); /* offset: start at 1st byte */
ByteSize, /* how many bytes */
PROT_READ | PROT_WRITE, /* access protections */
MAP_SHARED, /* mapping visible to other processes */
fd, /* file descriptor */
0); /* offset: start at 1st byte */
if ((caddr_t) -1 == memptr) report_and_exit("Can't get segment...");
[fprintf][7](stderr, "shared mem address: %p [0..%d]\n", memptr, ByteSize - 1);
[fprintf][7](stderr, "backing file: /dev/shm%s\n", BackingFile );
fprintf(stderr, "shared mem address: %p [0..%d]\n", memptr, ByteSize - 1);
fprintf(stderr, "backing file: /dev/shm%s\n", BackingFile );
/* semahore code to lock the shared mem */
/* semaphore code to lock the shared mem */
sem_t* semptr = sem_open(SemaphoreName, /* name */
O_CREAT, /* create the semaphore */
AccessPerms, /* protection perms */
0); /* initial value */
O_CREAT, /* create the semaphore */
AccessPerms, /* protection perms */
0); /* initial value */
if (semptr == (void*) -1) report_and_exit("sem_open");
[strcpy][8](memptr, MemContents); /* copy some ASCII bytes to the segment */
strcpy(memptr, MemContents); /* copy some ASCII bytes to the segment */
/* increment the semaphore so that memreader can read */
if (sem_post(semptr) < 0) report_and_exit("sem_post");
@ -341,8 +336,8 @@ munmap(memptr, ByteSize); /* unmap the storage *
#include "shmem.h"
void report_and_exit(const char* msg) {
[perror][4](msg);
[exit][5](-1);
perror(msg);
exit(-1);
}
int main() {
@ -351,24 +346,24 @@ int main() {
/* get a pointer to memory */
caddr_t memptr = mmap(NULL, /* let system pick where to put segment */
ByteSize, /* how many bytes */
PROT_READ | PROT_WRITE, /* access protections */
MAP_SHARED, /* mapping visible to other processes */
fd, /* file descriptor */
0); /* offset: start at 1st byte */
ByteSize, /* how many bytes */
PROT_READ | PROT_WRITE, /* access protections */
MAP_SHARED, /* mapping visible to other processes */
fd, /* file descriptor */
0); /* offset: start at 1st byte */
if ((caddr_t) -1 == memptr) report_and_exit("Can't access segment...");
/* create a semaphore for mutual exclusion */
sem_t* semptr = sem_open(SemaphoreName, /* name */
O_CREAT, /* create the semaphore */
AccessPerms, /* protection perms */
0); /* initial value */
O_CREAT, /* create the semaphore */
AccessPerms, /* protection perms */
0); /* initial value */
if (semptr == (void*) -1) report_and_exit("sem_open");
/* use semaphore as a mutex (lock) by waiting for writer to increment it */
if (!sem_wait(semptr)) { /* wait until semaphore != 0 */
int i;
for (i = 0; i < [strlen][6](MemContents); i++)
for (i = 0; i < strlen(MemContents); i++)
write(STDOUT_FILENO, memptr + i, 1); /* one byte at a time */
sem_post(semptr);
}

81
published/20190416 Inter-process communication in Linux- Using pipes and message queues.md
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@ -87,8 +87,8 @@ world
#define WriteEnd 1
void report_and_exit(const char* msg) {
[perror][6](msg);
[exit][7](-1); /** failure **/
perror(msg);
exit(-1); /** failure **/
}
int main() {
@ -112,11 +112,11 @@ int main() {
else { /*** parent ***/
close(pipeFDs[ReadEnd]); /* parent writes, doesn't read */
write(pipeFDs[WriteEnd], msg, [strlen][8](msg)); /* write the bytes to the pipe */
write(pipeFDs[WriteEnd], msg, strlen(msg)); /* write the bytes to the pipe */
close(pipeFDs[WriteEnd]); /* done writing: generate eof */
wait(NULL); /* wait for child to exit */
[exit][7](0); /* exit normally */
exit(0); /* exit normally */
}
return 0;
}
@ -249,7 +249,7 @@ bye, bye ## ditto
```c
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
#include <stdlib.h>
@ -264,24 +264,24 @@ int main() {
const char* pipeName = "./fifoChannel";
mkfifo(pipeName, 0666); /* read/write for user/group/others */
int fd = open(pipeName, O_CREAT | O_WRONLY); /* open as write-only */
if (fd < 0) return -1; /** error **/
if (fd < 0) return -1; /* can't go on */
int i;
for (i = 0; i < MaxLoops; i++) { /* write MaxWrites times */
int j;
for (j = 0; j < ChunkSize; j++) { /* each time, write ChunkSize bytes */
int k;
int chunk[IntsPerChunk];
for (k = 0; k < IntsPerChunk; k++)
chunk[k] = [rand][9]();
write(fd, chunk, sizeof(chunk));
for (k = 0; k < IntsPerChunk; k++)
chunk[k] = rand();
write(fd, chunk, sizeof(chunk));
}
usleep(([rand][9]() % MaxZs) + 1); /* pause a bit for realism */
usleep((rand() % MaxZs) + 1); /* pause a bit for realism */
}
close(fd); /* close pipe: generates an end-of-file */
unlink(pipeName); /* unlink from the implementing file */
[printf][10]("%i ints sent to the pipe.\n", MaxLoops * ChunkSize * IntsPerChunk);
close(fd); /* close pipe: generates an end-of-stream marker */
unlink(pipeName); /* unlink from the implementing file */
printf("%i ints sent to the pipe.\n", MaxLoops * ChunkSize * IntsPerChunk);
return 0;
}
@ -318,13 +318,12 @@ unlink(pipeName); /* unlink from the implementing file */
#include <fcntl.h>
#include <unistd.h>
unsigned is_prime(unsigned n) { /* not pretty, but gets the job done efficiently */
unsigned is_prime(unsigned n) { /* not pretty, but efficient */
if (n <= 3) return n > 1;
if (0 == (n % 2) || 0 == (n % 3)) return 0;
unsigned i;
for (i = 5; (i * i) <= n; i += 6)
for (i = 5; (i * i) <= n; i += 6)
if (0 == (n % i) || 0 == (n % (i + 2))) return 0;
return 1; /* found a prime! */
@ -332,25 +331,25 @@ unsigned is_prime(unsigned n) { /* not pretty, but gets the job done efficiently
int main() {
const char* file = "./fifoChannel";
int fd = open(file, O_RDONLY);
int fd = open(file, O_RDONLY);
if (fd < 0) return -1; /* no point in continuing */
unsigned count = 0, total = 0, primes_count = 0;
while (1) {
int next;
int i;
ssize_t count = read(fd, &next, sizeof(int));
ssize_t count = read(fd, &next, sizeof(int));
if (0 == count) break; /* end of stream */
else if (count == sizeof(int)) { /* read a 4-byte int value */
total++;
if (is_prime(next)) primes_count++;
}
}
}
close(fd); /* close pipe from read end */
unlink(file); /* unlink from the underlying file */
[printf][10]("Received ints: %u, primes: %u\n", total, primes_count);
printf("Received ints: %u, primes: %u\n", total, primes_count);
return 0;
}
@ -434,23 +433,23 @@ ID `qid` 在效果上是消息队列文件描述符的对应物。
#### 示例 5. sender 程序
```c
#include <stdio.h>
#include <sys/ipc.h>
#include <stdio.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <stdlib.h>
#include <string.h>
#include "queue.h"
void report_and_exit(const char* msg) {
[perror][6](msg);
[exit][7](-1); /* EXIT_FAILURE */
perror(msg);
exit(-1); /* EXIT_FAILURE */
}
int main() {
key_t key = ftok(PathName, ProjectId);
key_t key = ftok(PathName, ProjectId);
if (key < 0) report_and_exit("couldn't get key...");
int qid = msgget(key, 0666 | IPC_CREAT);
int qid = msgget(key, 0666 | IPC_CREAT);
if (qid < 0) report_and_exit("couldn't get queue id...");
char* payloads[] = {"msg1", "msg2", "msg3", "msg4", "msg5", "msg6"};
@ -460,11 +459,11 @@ int main() {
/* build the message */
queuedMessage msg;
msg.type = types[i];
[strcpy][11](msg.payload, payloads[i]);
strcpy(msg.payload, payloads[i]);
/* send the message */
msgsnd(qid, &msg, sizeof(msg), IPC_NOWAIT); /* don't block */
[printf][10]("%s sent as type %i\n", msg.payload, (int) msg.type);
printf("%s sent as type %i\n", msg.payload, (int) msg.type);
}
return 0;
}
@ -481,21 +480,21 @@ msgsnd(qid, &msg, sizeof(msg), IPC_NOWAIT);
#### 示例 6. receiver 程序
```c
#include <stdio.h>
#include <sys/ipc.h>
#include <stdio.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <stdlib.h>
#include "queue.h"
void report_and_exit(const char* msg) {
[perror][6](msg);
[exit][7](-1); /* EXIT_FAILURE */
perror(msg);
exit(-1); /* EXIT_FAILURE */
}
int main() {
int main() {
key_t key= ftok(PathName, ProjectId); /* key to identify the queue */
if (key < 0) report_and_exit("key not gotten...");
int qid = msgget(key, 0666 | IPC_CREAT); /* access if created already */
if (qid < 0) report_and_exit("no access to queue...");
@ -504,15 +503,15 @@ int main() {
for (i = 0; i < MsgCount; i++) {
queuedMessage msg; /* defined in queue.h */
if (msgrcv(qid, &msg, sizeof(msg), types[i], MSG_NOERROR | IPC_NOWAIT) < 0)
[puts][12]("msgrcv trouble...");
[printf][10]("%s received as type %i\n", msg.payload, (int) msg.type);
puts("msgrcv trouble...");
printf("%s received as type %i\n", msg.payload, (int) msg.type);
}
/** remove the queue **/
if (msgctl(qid, IPC_RMID, NULL) < 0) /* NULL = 'no flags' */
report_and_exit("trouble removing queue...");
return 0;
return 0;
}
```