Reformat code

.clang-format

@@ -0,0 +1,16 @@
+BasedOnStyle: LLVM
+IndentWidth: 8
+TabWidth: 8
+UseTab: Always
+BreakBeforeBraces: Linux
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: InlineOnly
+ColumnLimit: 80
+AlignConsecutiveDeclarations: false
+AlignConsecutiveAssignments: false
+AlignEscapedNewlines: Left
+AlignOperands: false
+IndentCaseLabels: false
+SpaceBeforeParens: ControlStatements
+

README.md

@@ -9,6 +9,7 @@ Welcome! This is a collection of chapter summaries from the book **Linux System
 - [Chapter 3 – Buffered I/O](chp3/README.md)
 - [Chapter 4 – Advanced File I/O](chp4/README.md)
 - [Chapter 5 - Process Management](chp5/README.md)
+- [Chapter 6 - Advanced Process Management](chp6/README.md)
 - [Exercises](exercises/README.md)
 
 > Each file contains an English summary of the chapter's key concepts.

chp1/syscalls/example1.c

@@ -2,8 +2,9 @@
 #include <stdlib.h>
 #include <unistd.h>
 
-int main(void) {
-  int fd = open("test.txt", O_CREAT | O_RDWR);
-  // close(fd);
-  return EXIT_SUCCESS;
+int main(void)
+{
+	int fd = open("test.txt", O_CREAT | O_RDWR);
+	// close(fd);
+	return EXIT_SUCCESS;
 }

chp2/fopenflags.c

@@ -1,7 +1,7 @@
-#include <stdio.h>
-#include <fcntl.h>
-#include <unistd.h>
 #include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
 
 int main(void)
 {
@@ -20,7 +20,7 @@ int main(void)
 	if (fd == -1)
 		perror("Third open");
 	close(fd);
-	
+
 	fd = open("test.txt", O_CREAT);
 	if (fd == -1)
 		perror("Fourth open");

chp2/fopenmode.c

@@ -1,12 +1,13 @@
-#include <stdio.h>
-#include <fcntl.h>
-#include <unistd.h>
 #include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
 
 int main(void)
 {
 	int fd;
-	fd = open("test.txt", O_CREAT | O_EXCL, S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH);
+	fd = open("test.txt", O_CREAT | O_EXCL,
+		  S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH);
 	if (fd == -1)
 		perror("open");
 	close(fd);

chp2/fpread.c

@@ -6,51 +6,56 @@
 #define _XOPEN_SOURCE 500
 #include <unistd.h>
 
-int main(void) {
-  printf("Try to open file read.txt\n");
-  int fd = open("read.txt", O_RDONLY);
-  if (fd == -1) {
-    perror("Failed to open read.txt");
-    return -1;
-  }
-  printf("Open file success\n");
+int main(void)
+{
+	printf("Try to open file read.txt\n");
+	int fd = open("read.txt", O_RDONLY);
+	if (fd == -1) {
+		perror("Failed to open read.txt");
+		return -1;
+	}
+	printf("Open file success\n");
 
-  int len;
-  // move file's cursor at the end of file and return bytes
-  if ((len = lseek(fd, 0, SEEK_END)) == -1) {
-    perror("Failed to move cursor at end of read.txt file");
-    return -1;
-  }
+	int len;
+	// move file's cursor at the end of file and return bytes
+	if ((len = lseek(fd, 0, SEEK_END)) == -1) {
+		perror("Failed to move cursor at end of read.txt file");
+		return -1;
+	}
 
-  // cannot rewind cursor at the start file because pread use "bytes_read_total" for position
+	// cannot rewind cursor at the start file because pread use
+	// "bytes_read_total" for position
 
-  printf("File size of %d bytes\n", len);
+	printf("File size of %d bytes\n", len);
 
-  printf("Reading file read.txt\n");
-  char buf[len + 1];
-  memset(buf, 0, sizeof(buf));
+	printf("Reading file read.txt\n");
+	char buf[len + 1];
+	memset(buf, 0, sizeof(buf));
 
-  size_t bytes_read_total = 0;
-  ssize_t ret;
-  while (bytes_read_total < len && (ret = pread(fd, buf, len - bytes_read_total, bytes_read_total)) != -1) {
-    if (ret == -1) {
-      if (errno == EINTR) continue;
-      perror("Failed to read read.txt");
-      break;
-    }
-    bytes_read_total += ret;
-  }
+	size_t bytes_read_total = 0;
+	ssize_t ret;
+	while (bytes_read_total < len &&
+	       (ret = pread(fd, buf, len - bytes_read_total,
+			    bytes_read_total)) != -1) {
+		if (ret == -1) {
+			if (errno == EINTR)
+				continue;
+			perror("Failed to read read.txt");
+			break;
+		}
+		bytes_read_total += ret;
+	}
 
-  buf[bytes_read_total] = '\0';
+	buf[bytes_read_total] = '\0';
 
-  printf("File text is:\n\"%s\"\n", buf);
+	printf("File text is:\n\"%s\"\n", buf);
 
-  printf("Close file read.txt\n");
-  
-  if (close(fd) == -1) {
-    perror("Failed to close read.txt");
-    return -1;
-  }
+	printf("Close file read.txt\n");
 
-  return 0;
+	if (close(fd) == -1) {
+		perror("Failed to close read.txt");
+		return -1;
+	}
+
+	return 0;
 }

chp2/fread.c

@@ -5,51 +5,55 @@
 #include <string.h>
 #include <unistd.h>
 
-int main(void) {
-  printf("Try to open file read.txt\n");
-  int fd = open("read.txt", O_RDONLY);
-  if (fd == -1) {
-    perror("Failed to open read.txt");
-    return -1;
-  }
-  printf("Open file success\n");
+int main(void)
+{
+	printf("Try to open file read.txt\n");
+	int fd = open("read.txt", O_RDONLY);
+	if (fd == -1) {
+		perror("Failed to open read.txt");
+		return -1;
+	}
+	printf("Open file success\n");
 
-  int len;
-  if ((len = lseek(fd, 0, SEEK_END)) == -1) {
-    perror("Failed to move cursor at end of read.txt file");
-    return -1;
-  }
-  printf("File size of %d bytes\n", len);
-  if (lseek(fd, 0, SEEK_SET) == -1) {
-    perror("Failed to move cursor at start of read.txt file");
-    return -1;
-  }
+	int len;
+	if ((len = lseek(fd, 0, SEEK_END)) == -1) {
+		perror("Failed to move cursor at end of read.txt file");
+		return -1;
+	}
+	printf("File size of %d bytes\n", len);
+	if (lseek(fd, 0, SEEK_SET) == -1) {
+		perror("Failed to move cursor at start of read.txt file");
+		return -1;
+	}
 
-  printf("Reading file read.txt\n");
-  char buf[len + 1];
-  memset(buf, 0, sizeof(buf));
+	printf("Reading file read.txt\n");
+	char buf[len + 1];
+	memset(buf, 0, sizeof(buf));
 
-  size_t bytes_read_total = 0;
-  ssize_t ret;
-  while (bytes_read_total < len && (ret = read(fd, buf + bytes_read_total, len - bytes_read_total)) != 0) {
-    if (ret == -1) {
-      if (errno == EINTR) continue;
-      perror("Failed to read read.txt");
-      break;
-    }
-    bytes_read_total += ret;
-  }
+	size_t bytes_read_total = 0;
+	ssize_t ret;
+	while (bytes_read_total < len &&
+	       (ret = read(fd, buf + bytes_read_total,
+			   len - bytes_read_total)) != 0) {
+		if (ret == -1) {
+			if (errno == EINTR)
+				continue;
+			perror("Failed to read read.txt");
+			break;
+		}
+		bytes_read_total += ret;
+	}
 
-  buf[bytes_read_total] = '\0';
+	buf[bytes_read_total] = '\0';
 
-  printf("File text is:\n\"%s\"\n", buf);
+	printf("File text is:\n\"%s\"\n", buf);
 
-  printf("Close file read.txt\n");
-  
-  if (close(fd) == -1) {
-    perror("Failed to close read.txt");
-    return -1;
-  }
+	printf("Close file read.txt\n");
 
-  return 0;
+	if (close(fd) == -1) {
+		perror("Failed to close read.txt");
+		return -1;
+	}
+
+	return 0;
 }

chp2/ftruncate.c

@@ -1,7 +1,8 @@
-#include <unistd.h>
 #include <stdio.h>
+#include <unistd.h>
 
-int main(void) {
+int main(void)
+{
 	int ret;
 
 	ret = truncate("./pirate.txt", 45);

chp2/poll.c

@@ -1,10 +1,11 @@
+#include <poll.h>
 #include <stdio.h>
 #include <unistd.h>
-#include <poll.h>
 
-#define TIMEOUT 5  /* poll timeout, in seconds */
+#define TIMEOUT 5 /* poll timeout, in seconds */
 
-int main(void) {
+int main(void)
+{
 	struct pollfd fds[2];
 	int ret;
 
@@ -30,7 +31,7 @@ int main(void) {
 
 	if (fds[0].revents & POLLIN)
 		printf("stdin is readable\n");
-	
+
 	if (fds[1].revents & POLLOUT)
 		printf("stdout is writable\n");
 

chp2/select.c

@@ -6,7 +6,8 @@
 #define TIMEOUT 5
 #define BUF_LEN 1024
 
-int main(void) {
+int main(void)
+{
 	struct timeval tv;
 	fd_set readfds;
 	int ret;
@@ -14,19 +15,13 @@ int main(void) {
 	/* Wait on stdin for intput. */
 	FD_ZERO(&readfds);
 	FD_SET(STDIN_FILENO, &readfds);
-	
+
 	/* Wait up to file seconds */
 	tv.tv_sec = TIMEOUT;
 	tv.tv_usec = 0;
 
 	/* All right, now block! */
-	ret = select(
-		STDIN_FILENO + 1,
-		&readfds,
-		NULL,
-		NULL,
-		&tv
-	);
+	ret = select(STDIN_FILENO + 1, &readfds, NULL, NULL, &tv);
 	if (ret == -1) {
 		perror("select");
 		return 1;
@@ -42,7 +37,7 @@ int main(void) {
 	 * nonzero, but we will humor ourselves.)
 	 */
 	if (FD_ISSET(STDIN_FILENO, &readfds)) {
-		char buf[BUF_LEN+1];
+		char buf[BUF_LEN + 1];
 		int len;
 
 		/* guaranteed to not block */
@@ -56,7 +51,7 @@ int main(void) {
 			buf[len] = '\0';
 			printf("read: %s\n", buf);
 		}
-		
+
 		return 0;
 	}
 

chp2/select_regular_files.c

@@ -1,11 +1,11 @@
+#include <errno.h>
+#include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <fcntl.h>
-#include <unistd.h>
-#include <errno.h>
 #include <string.h>
-#include <sys/time.h>
 #include <sys/select.h>
+#include <sys/time.h>
+#include <unistd.h>
 
 #define FILE_NUMBER 3
 #define FILENAME_MAX_LEN 10
@@ -15,7 +15,8 @@
 int create_tmp_file(char *filename);
 void cleanup(char *filenames[]);
 
-int main(void) {
+int main(void)
+{
 	int exit_code = 0;
 	char *filename_template = "test%d.txt";
 	char *filenames[FILE_NUMBER] = {NULL};
@@ -23,48 +24,47 @@ int main(void) {
 
 	// Create a bunch of number ephemeral files
 	for (int i = 0; i < FILE_NUMBER; i++) {
-		char *filename = (char *)malloc(FILENAME_MAX_LEN*sizeof(char)); 
+		char *filename =
+		    (char *)malloc(FILENAME_MAX_LEN * sizeof(char));
 		if (!filename) {
 			perror("malloc failed");
 			exit_code = -1;
 			goto exit;
 		}
-		snprintf(filename, FILENAME_MAX_LEN, filename_template, i+1);
+		snprintf(filename, FILENAME_MAX_LEN, filename_template, i + 1);
 		filenames[i] = filename;
 		printf("Opening file %s...\n", filename);
 		fds[i] = create_tmp_file(filename);
 		if (fds[i] == -1) {
-			fprintf(stderr, "Error to open file %s: %s\n", filename, strerror(errno));
+			fprintf(stderr, "Error to open file %s: %s\n", filename,
+				strerror(errno));
 			exit_code = -1;
 			goto exit;
 		}
-		printf("Open file %s with file descriptor %d\n", filename, fds[i]);
+		printf("Open file %s with file descriptor %d\n", filename,
+		       fds[i]);
 
 		// write something in the files
 		dprintf(fds[i], "Hello I am %s\n", filename);
 	}
-	
+
 	fd_set readfds;
 	FD_ZERO(&readfds);
 	for (int i = 0; i < FILE_NUMBER; i++) {
 		FD_SET(fds[i], &readfds);
 	}
-	
-	struct timeval *timeout = (struct timeval *)malloc(sizeof(struct timeval));
+
+	struct timeval *timeout =
+	    (struct timeval *)malloc(sizeof(struct timeval));
 	timeout->tv_sec = TIMEOUT;
 	timeout->tv_usec = 0;
-	
-	/* This function do not work with regular files because for the operating system,
-	 * a regular file is ready always.
-         * This example is wrong the best way to use select() is with socket, pipe or other channel types.
+
+	/* This function do not work with regular files because for the
+	 * operating system, a regular file is ready always. This example is
+	 * wrong the best way to use select() is with socket, pipe or other
+	 * channel types.
 	 */
-	int ret = select(
-		FILE_NUMBER + 1,
-		&readfds,
-		NULL,
-		NULL,
-		timeout
-	);
+	int ret = select(FILE_NUMBER + 1, &readfds, NULL, NULL, timeout);
 
 	if (ret == -1) {
 		fprintf(stderr, "Error to select: %s\n", strerror(errno));
@@ -79,10 +79,11 @@ int main(void) {
 	for (int i = 0; i < FILE_NUMBER; i++) {
 		int fd = fds[i];
 		if (FD_ISSET(fd, &readfds)) {
-			char buf[BUF_LEN+1];
+			char buf[BUF_LEN + 1];
 			int len = read(fd, buf, BUF_LEN);
 			if (len == -1) {
-				fprintf(stderr, "Error reading file %s: %s\n", filenames[i], strerror(errno));
+				fprintf(stderr, "Error reading file %s: %s\n",
+					filenames[i], strerror(errno));
 				exit_code = 1;
 				goto exit;
 			}
@@ -98,8 +99,9 @@ exit:
 	for (int i = 0; i < FILE_NUMBER; i++) {
 		int fd = fds[i];
 		printf("Close file with file descriptor %d\n", fd);
-		if (close(fd) == -1) { 
-			fprintf(stderr, "Error to close file %d: %s\n", fd, strerror(errno));
+		if (close(fd) == -1) {
+			fprintf(stderr, "Error to close file %d: %s\n", fd,
+				strerror(errno));
 		}
 	}
 
@@ -108,11 +110,12 @@ exit:
 
 	printf("Cleanup files\n");
 	cleanup(filenames);
-	
+
 	return exit_code;
 }
 
-int create_tmp_file(char *filename) {
+int create_tmp_file(char *filename)
+{
 	int fd = open(filename, O_CREAT | O_EXCL | O_RDWR, 0644);
 	if (fd == -1) {
 		return -1;
@@ -120,11 +123,13 @@ int create_tmp_file(char *filename) {
 	return fd;
 }
 
-void cleanup(char *filenames[]) {
+void cleanup(char *filenames[])
+{
 	for (int j = 0; j < FILE_NUMBER; j++) {
 		if (filenames[j] != NULL) {
-			if (remove(filenames[j]) == -1) 
-				fprintf(stderr, "Failed to remove %s: %s\n", filenames[j], strerror(errno));
+			if (remove(filenames[j]) == -1)
+				fprintf(stderr, "Failed to remove %s: %s\n",
+					filenames[j], strerror(errno));
 			free(filenames[j]);
 			filenames[j] = NULL;
 		}

chp3/binarydata.c

@@ -1,40 +1,42 @@
 #include <stdio.h>
 
-int main(void) {
-    FILE *in, *out;
-    struct pirate {
-        char name[100];         /* real name */
-        unsigned long booty;    /* in pounds sterling */
-        unsigned int beard_len; /* in inches */
-    } p, blackbeard = {"Edward Teach", 950, 48};
+int main(void)
+{
+	FILE *in, *out;
+	struct pirate {
+		char name[100];		/* real name */
+		unsigned long booty;	/* in pounds sterling */
+		unsigned int beard_len; /* in inches */
+	} p, blackbeard = {"Edward Teach", 950, 48};
 
-    out = fopen("data", "w");
-    if (!out) {
-        perror("fopen");
-        return 1;
-    }
-    if (!fwrite(&blackbeard, sizeof(struct pirate), 1, out)) {
-        perror("fwrite");
-        return 1;
-    }
-    if (fclose(out)) {
-        perror("fclose");
-        return 1;
-    }
+	out = fopen("data", "w");
+	if (!out) {
+		perror("fopen");
+		return 1;
+	}
+	if (!fwrite(&blackbeard, sizeof(struct pirate), 1, out)) {
+		perror("fwrite");
+		return 1;
+	}
+	if (fclose(out)) {
+		perror("fclose");
+		return 1;
+	}
 
-    in = fopen("data", "r");
-    if (!in) {
-        perror("fopen");
-        return 1;
-    }
-    if (!fread(&p, sizeof(struct pirate), 1, in)) {
-        perror("fread");
-        return 1;
-    }
-    if (fclose(in)) {
-        perror("fclose");
-        return 1;
-    }
-    printf("name=\"%s\" booty=%lu beard_len=%u\n", p.name, p.booty, p.beard_len);
-    return 0;
+	in = fopen("data", "r");
+	if (!in) {
+		perror("fopen");
+		return 1;
+	}
+	if (!fread(&p, sizeof(struct pirate), 1, in)) {
+		perror("fread");
+		return 1;
+	}
+	if (fclose(in)) {
+		perror("fclose");
+		return 1;
+	}
+	printf("name=\"%s\" booty=%lu beard_len=%u\n", p.name, p.booty,
+	       p.beard_len);
+	return 0;
 }

chp3/input.c

@@ -1,7 +1,8 @@
-#include<stdio.h>
 #include <limits.h>
+#include <stdio.h>
 
-int main(void) {
-    printf("Limit buffer size is %u bytes.\n", LINE_MAX);
-    printf("Buffer size is %u bytes.\n", BUFSIZ);
+int main(void)
+{
+	printf("Limit buffer size is %u bytes.\n", LINE_MAX);
+	printf("Buffer size is %u bytes.\n", BUFSIZ);
 }

chp4/blocks.c

@@ -1,10 +1,10 @@
+#include <fcntl.h>
+#include <linux/fs.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <fcntl.h>
-#include <sys/types.h>
-#include <sys/stat.h>
 #include <sys/ioctl.h>
-#include <linux/fs.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 
 /* get_block - for the file associated with the given fd, returns
  * the physical block mapping to logical_block
@@ -22,66 +22,71 @@ int get_nr_blocks(int fd);
  */
 void print_blocks(int fd);
 
-int main(int argc, char *argv[]) {
-    if (argc < 2) {
-        fprintf(stderr, "usage: %s <file>\n", argv[0]);
-        return 1;
-    }
+int main(int argc, char *argv[])
+{
+	if (argc < 2) {
+		fprintf(stderr, "usage: %s <file>\n", argv[0]);
+		return 1;
+	}
 
-    int fd = open(argv[1], O_RDONLY);
-    if (fd < 0) {
-        perror("open");
-        return 1;
-    }
+	int fd = open(argv[1], O_RDONLY);
+	if (fd < 0) {
+		perror("open");
+		return 1;
+	}
 
-    print_blocks(fd);
-    return 0;
+	print_blocks(fd);
+	return 0;
 }
 
-int get_block(int fd, int logical_block) {
-    int ret = ioctl(fd, FIBMAP, &logical_block);
-    if (ret < 0) {
-        perror("ioctl");
-        return -1;
-    }
-    return logical_block;
+int get_block(int fd, int logical_block)
+{
+	int ret = ioctl(fd, FIBMAP, &logical_block);
+	if (ret < 0) {
+		perror("ioctl");
+		return -1;
+	}
+	return logical_block;
 }
 
-int get_nr_blocks(int fd) {
-    struct stat buf;
-    int ret = fstat(fd, &buf);
-    if (ret < 0) {
-        perror("fstat");
-        return -1;
-    }
-    return buf.st_blocks;
+int get_nr_blocks(int fd)
+{
+	struct stat buf;
+	int ret = fstat(fd, &buf);
+	if (ret < 0) {
+		perror("fstat");
+		return -1;
+	}
+	return buf.st_blocks;
 }
 
-void print_blocks(int fd) {
-    int nr_blocks = get_nr_blocks(fd);
-    if (nr_blocks < 0) {
-        fprintf(stderr, "get_nr_blocks failed!\n");
-        return;
-    }
+void print_blocks(int fd)
+{
+	int nr_blocks = get_nr_blocks(fd);
+	if (nr_blocks < 0) {
+		fprintf(stderr, "get_nr_blocks failed!\n");
+		return;
+	}
 
-    if (nr_blocks == 0) {
-        printf("no allocated blocks\n");
-        return;
-    } else if (nr_blocks == 1) {
-        printf("1 block\n");
-    } else {
-        printf("%d blocks\n\n", nr_blocks);
-    }
+	if (nr_blocks == 0) {
+		printf("no allocated blocks\n");
+		return;
+	} else if (nr_blocks == 1) {
+		printf("1 block\n");
+	} else {
+		printf("%d blocks\n\n", nr_blocks);
+	}
 
-    for (int i = 0; i < nr_blocks; i++) {
-        int phys_block = get_block(fd, i);
-        if (phys_block < 0) {
-            fprintf(stderr, "get_block failed!\n");
-            return;
-        }
-        if (!phys_block) continue;
+	for (int i = 0; i < nr_blocks; i++) {
+		int phys_block = get_block(fd, i);
+		if (phys_block < 0) {
+			fprintf(stderr, "get_block failed!\n");
+			return;
+		}
+		if (!phys_block)
+			continue;
 
-        printf("(%u, %u) ", i, phys_block);
-    }
-    putchar('\n');
+		printf("(%u, %u) ", i, phys_block);
+	}
+	putchar('\n');
 }

chp4/inode.c

@@ -1,39 +1,41 @@
+#include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <fcntl.h>
-#include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/types.h>
 
 /* get_inode - returns the inode of the file associated
  * with the given file descriptor, or -1 on failure.
  */
 int get_inode(int fd);
 
-int main(int argc, char *argv[]) {
-    if (argc < 2) {
-        fprintf(stderr, "usage: %s <file>\n", argv[0]);
-        return 1;
-    }
+int main(int argc, char *argv[])
+{
+	if (argc < 2) {
+		fprintf(stderr, "usage: %s <file>\n", argv[0]);
+		return 1;
+	}
 
-    int fd = open(argv[1], O_RDONLY);
-    if (fd < 0) {
-        perror("open");
-        return 1;
-    }
+	int fd = open(argv[1], O_RDONLY);
+	if (fd < 0) {
+		perror("open");
+		return 1;
+	}
 
-    int inode = get_inode(fd);
-    printf("%d\n", inode);
-    
-    return 0;
+	int inode = get_inode(fd);
+	printf("%d\n", inode);
+
+	return 0;
 }
 
-int get_inode(int fd) {
-    struct stat buf;
+int get_inode(int fd)
+{
+	struct stat buf;
 
-    int ret = fstat(fd, &buf);
-    if (ret < 0) {
-        perror("fstat");
-        return -1;
-    }
-    return buf.st_ino;
+	int ret = fstat(fd, &buf);
+	if (ret < 0) {
+		perror("fstat");
+		return -1;
+	}
+	return buf.st_ino;
 }

chp4/mmap.c

@@ -1,12 +1,13 @@
-#include <stdio.h>
-#include <sys/types.h>
-#include <sys/stat.h>
 #include <fcntl.h>
-#include <unistd.h>
+#include <stdio.h>
 #include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[])
+{
 
-int main(int argc, char *argv[]) {
-	
 	if (argc < 2) {
 		fprintf(stderr, "usage: %s <file>\n", argv[0]);
 		return 1;

chp4/readv.c

@@ -1,41 +1,42 @@
-#include <stdio.h>
-#include <sys/types.h>
-#include <sys/stat.h>
 #include <fcntl.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <sys/uio.h>
 #include <unistd.h>
 
-int main(void) {
-    char foo[48], bar[51], baz[49];
-    int fd = open("buccaneer.txt", O_RDONLY);
-    if (fd == -1) {
-        perror("open");
-        return 1;
-    }
+int main(void)
+{
+	char foo[48], bar[51], baz[49];
+	int fd = open("buccaneer.txt", O_RDONLY);
+	if (fd == -1) {
+		perror("open");
+		return 1;
+	}
 
-    // setup our iovec structures
-    struct iovec iov[3];
-    iov[0].iov_base = foo;
-    iov[0].iov_len = sizeof(foo);
-    iov[1].iov_base = bar;
-    iov[1].iov_len = sizeof(bar);
-    iov[2].iov_base = baz;
-    iov[2].iov_len = sizeof(baz);
+	// setup our iovec structures
+	struct iovec iov[3];
+	iov[0].iov_base = foo;
+	iov[0].iov_len = sizeof(foo);
+	iov[1].iov_base = bar;
+	iov[1].iov_len = sizeof(bar);
+	iov[2].iov_base = baz;
+	iov[2].iov_len = sizeof(baz);
 
-    // read into the structures with a single call
-    int nr = readv(fd, iov, 3);
-    if (nr == -1) {
-        perror("readv");
-        return 1;
-    }
+	// read into the structures with a single call
+	int nr = readv(fd, iov, 3);
+	if (nr == -1) {
+		perror("readv");
+		return 1;
+	}
 
-    for (int i = 0; i < 3; i++)
-        printf("%d: %s", i, (char *)iov[i].iov_base);
+	for (int i = 0; i < 3; i++)
+		printf("%d: %s", i, (char *)iov[i].iov_base);
 
-    if (close(fd)) {
-        perror("close");
-        return 1;
-    }
+	if (close(fd)) {
+		perror("close");
+		return 1;
+	}
 
-    return 0;
+	return 0;
 }

chp4/writev.c

@@ -1,45 +1,44 @@
-#include <stdio.h>
-#include <sys/types.h>
-#include <sys/stat.h>
 #include <fcntl.h>
+#include <stdio.h>
 #include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <sys/uio.h>
 #include <unistd.h>
 
-int main(void) {
-    struct iovec iov[3];
+int main(void)
+{
+	struct iovec iov[3];
 
-    char *buf[] = {
-        "The term buccaneer comes from the word boucan.\n",
-        "A boucan is a wooden frame used for cooking meet.\n",
-        "Buccaneer is the West Indies name for a pirate.\n"
-    };
+	char *buf[] = {"The term buccaneer comes from the word boucan.\n",
+		       "A boucan is a wooden frame used for cooking meet.\n",
+		       "Buccaneer is the West Indies name for a pirate.\n"};
 
-    int fd = open("buccaneer.txt", O_WRONLY | O_CREAT | O_TRUNC);
-    if (fd == -1) {
-        perror("open");
-        return 1;
-    }
+	int fd = open("buccaneer.txt", O_WRONLY | O_CREAT | O_TRUNC);
+	if (fd == -1) {
+		perror("open");
+		return 1;
+	}
 
-    // fill out three iovec structures
-    for (int i = 0; i < 3; i++) {
-        iov[i].iov_base = buf[i];
-        iov[i].iov_len = strlen(buf[i]) + 1;
-    }
+	// fill out three iovec structures
+	for (int i = 0; i < 3; i++) {
+		iov[i].iov_base = buf[i];
+		iov[i].iov_len = strlen(buf[i]) + 1;
+	}
 
-    // with a single call, write them all out
-    ssize_t nr = writev(fd, iov, 3);
-    if (nr == -1) {
-        perror("writev");
-        return 1;
-    }
+	// with a single call, write them all out
+	ssize_t nr = writev(fd, iov, 3);
+	if (nr == -1) {
+		perror("writev");
+		return 1;
+	}
 
-    printf("wrote %lu bytes\n", nr);
+	printf("wrote %lu bytes\n", nr);
 
-    if (close(fd)) {
-        perror("close");
-        return 1;
-    }
+	if (close(fd)) {
+		perror("close");
+		return 1;
+	}
 
-    return 0;
+	return 0;
 }

chp5/atexit.c

@@ -1,15 +1,16 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-void out(void) {
-    printf("atexit() succeeded!\n");
+void out(void)
+{
+	printf("atexit() succeeded!\n");
 }
 
-
-int main(void) {
-    if (atexit(out)) {
-        fprintf(stderr, "atexit() failed\n");
-        return 1;
-    }
-    return 0;
+int main(void)
+{
+	if (atexit(out)) {
+		fprintf(stderr, "atexit() failed\n");
+		return 1;
+	}
+	return 0;
 }

chp5/daemon.c

@@ -1,43 +1,46 @@
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <stdlib.h>
-#include <stdio.h>
 #include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <unistd.h>
 
 #define NR_OPEN 1048576
 
-int main(void) {
-    // create new process
-    pid_t pid = fork();
-    if (pid == -1) {
-        return -1;
-    } else if (pid != 0) {
-        printf("Running daemon with pid %d\n", pid);
-        exit(EXIT_SUCCESS);
-    }
+int main(void)
+{
+	// create new process
+	pid_t pid = fork();
+	if (pid == -1) {
+		return -1;
+	} else if (pid != 0) {
+		printf("Running daemon with pid %d\n", pid);
+		exit(EXIT_SUCCESS);
+	}
 
-    // create a new session and process group
-    if (setsid() == -1) return -1;
+	// create a new session and process group
+	if (setsid() == -1)
+		return -1;
 
-    // set the working directory to the root directory
-    if (chdir("/") == -1) return -1;
+	// set the working directory to the root directory
+	if (chdir("/") == -1)
+		return -1;
 
-    // close all open files--NR_OPEN is overkill, but works
-    for (int i = 0; i < NR_OPEN; i++) { 
-        close(i);
-    }
+	// close all open files--NR_OPEN is overkill, but works
+	for (int i = 0; i < NR_OPEN; i++) {
+		close(i);
+	}
 
-    // redirect fd's 0,1,2 to /dev/null
-    open("/dev/null", O_RDWR); // stdin
-    dup(0);                    // stdout
-    dup(0);                    // stderr
+	// redirect fd's 0,1,2 to /dev/null
+	open("/dev/null", O_RDWR); // stdin
+	dup(0);			   // stdout
+	dup(0);			   // stderr
 
-    // do its daemon thing
-    for (int i = 0; i < 10; i++) {
-        printf("Hello from daemon %d\n", getpid());
-        sleep(1000);
-    }
+	// do its daemon thing
+	for (int i = 0; i < 10; i++) {
+		printf("Hello from daemon %d\n", getpid());
+		sleep(1000);
+	}
 
-    return 0;
+	return 0;
 }

chp5/session.c

@@ -2,8 +2,9 @@
 #define _XOPEN_SOURCE 500
 #include <unistd.h>
 
-int main(void) {
-    printf("My session id=%d\n", getsid(0));
-    printf("My process group id=%d\n", getpgid(0));
-    return 0;
+int main(void)
+{
+	printf("My session id=%d\n", getsid(0));
+	printf("My process group id=%d\n", getpgid(0));
+	return 0;
 }

chp5/system.c

@@ -1,63 +1,65 @@
 #include <stdio.h>
 #define _XOPEN_SOURCE
 #include <stdlib.h>
-#include <unistd.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <unistd.h>
 
 /* my_system - synchronously spawns and waits for the command
  * "/bin/sh -c <cmd>".
- * 
+ *
  * Returns -1 on error of any sort, or the exit code from the
  * launched process. Does not block or ignore any signals.
  */
 int my_system(const char *);
 
-int main(int argc, char *argv[]) {
-    if (argc < 2) {
-        fprintf(stderr, "usage: %s <command>", argv[0]);
-        return EXIT_FAILURE;
-    }
-    
-    const char *command = argv[1];
-    pid_t pid = fork();
-    if (pid == -1) {
-        perror("fork");
-        return EXIT_FAILURE;
-    } else if (pid > 0) {
-        int ret = my_system(command);
-        if (ret == -1) {
-            fprintf(stderr, "command: \"%s\" error", command);
-            return EXIT_FAILURE;
-        }
-        return ret;
-    }
-    
-    int status;
-    wait(&status);
-    return status;
+int main(int argc, char *argv[])
+{
+	if (argc < 2) {
+		fprintf(stderr, "usage: %s <command>", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	const char *command = argv[1];
+	pid_t pid = fork();
+	if (pid == -1) {
+		perror("fork");
+		return EXIT_FAILURE;
+	} else if (pid > 0) {
+		int ret = my_system(command);
+		if (ret == -1) {
+			fprintf(stderr, "command: \"%s\" error", command);
+			return EXIT_FAILURE;
+		}
+		return ret;
+	}
+
+	int status;
+	wait(&status);
+	return status;
 }
 
-int my_system(const char *cmd) {
-    pid_t pid = fork();
-    if (pid == -1) {
-        return -1;
-    } else if (pid == 0) {
-        const char *argv[4];
-        argv[0] = "sh";
-        argv[1] = "-c";
-        argv[2] = cmd;
-        argv[3] = NULL;
+int my_system(const char *cmd)
+{
+	pid_t pid = fork();
+	if (pid == -1) {
+		return -1;
+	} else if (pid == 0) {
+		const char *argv[4];
+		argv[0] = "sh";
+		argv[1] = "-c";
+		argv[2] = cmd;
+		argv[3] = NULL;
 
-        execv("/bin/sh", argv);
-        exit(-1);
-    }
-    
-    int status;
-    if (waitpid(pid, &status, 0) == -1) {
-        return -1;
-    } else if (WIFEXITED(status)) {
-        return WEXITSTATUS(status);
-    }
-    return -1;
+		execv("/bin/sh", argv);
+		exit(-1);
+	}
+
+	int status;
+	if (waitpid(pid, &status, 0) == -1) {
+		return -1;
+	} else if (WIFEXITED(status)) {
+		return WEXITSTATUS(status);
+	}
+	return -1;
 }

chp5/wait.c

@@ -1,31 +1,34 @@
-#include <unistd.h>
 #include <stdio.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <unistd.h>
 
-int main(void) {
-    if (!fork())
-        return 1;
+int main(void)
+{
+	if (!fork())
+		return 1;
 
-    int status;
-    pid_t pid = wait(&status);
-    if (pid == -1) {
-        perror("wait");
-    }
+	int status;
+	pid_t pid = wait(&status);
+	if (pid == -1) {
+		perror("wait");
+	}
 
-    printf("pid=%d\n", pid);
-    
-    if (WIFEXITED(status))
-        printf("Normal termination with exit status=%d\n", WEXITSTATUS(status));
+	printf("pid=%d\n", pid);
 
-    if (WIFSIGNALED(status))
-        printf("Killed by signal=%d%s\n", WTERMSIG(status), WCOREDUMP(status) ? " (dumped core)" : "");
+	if (WIFEXITED(status))
+		printf("Normal termination with exit status=%d\n",
+		       WEXITSTATUS(status));
 
-    if (WIFSTOPPED(status))
-        printf("Stopped by signal=%d\n", WSTOPSIG(status));
+	if (WIFSIGNALED(status))
+		printf("Killed by signal=%d%s\n", WTERMSIG(status),
+		       WCOREDUMP(status) ? " (dumped core)" : "");
 
-    if (WIFCONTINUED(status))
-        printf("Continued\n");
+	if (WIFSTOPPED(status))
+		printf("Stopped by signal=%d\n", WSTOPSIG(status));
 
-    return 0;
+	if (WIFCONTINUED(status))
+		printf("Continued\n");
+
+	return 0;
 }

chp6/README.md

@@ -0,0 +1,52 @@
+# 📘 Chapter 6 – Advanced Process Management (Summary)
+**From _Linux System Programming_ by Robert Love, 2nd Ed.**
+
+---
+
+## 🔄 Process Scheduling
+- The kernel scheduler selects **runnable processes** (those not blocked on I/O, etc.).
+- Goals: **maximize CPU utilization**, minimize wait time, and ensure fairness :contentReference[oaicite:1]{index=1}.
+- Covers **preemptive scheduling**, **timeslices**, and the Linux **Completely Fair Scheduler (CFS)**.
+- Explains **processor affinity** and CPU sets: binding processes to specific CPUs for cache performance :contentReference[oaicite:2]{index=2}.
+
+## 🧭 Yielding the Processor
+- `sched_yield()` lets a running process give up the CPU voluntarily.
+- Useful in busy-wait loops or when expecting immediate CPU from others :contentReference[oaicite:3]{index=3}.
+
+## 🎚️ Priorities & Nice Values
+- Processes can adjust their priority using **`nice()`**, where lower nice = higher priority.
+- Real-time scheduling policies (`SCHED_FIFO`, `SCHED_RR`) grant stronger priority guarantees for time-sensitive tasks :contentReference[oaicite:4]{index=4}.
+
+## 🧠 Processor Affinity
+- **Get/set CPU affinity** with `sched_getaffinity()` and `sched_setaffinity()`.
+- Ensures cache affinity, reducing context-switch overhead :contentReference[oaicite:5]{index=5}.
+
+## ⏱️ Real-Time Scheduling
+- Differences between **hard** and **soft real-time** systems.
+- Configurable policies: `SCHED_FIFO`, `SCHED_RR`, with real-time priority range 0–99 :contentReference[oaicite:6]{index=6}.
+- Care needed: real-time tasks can lead to starvation of normal tasks.
+
+## 🔒 Resource Limits
+- Kernel enforces per-process limits via `setrlimit()`/`getrlimit()`:
+  - CPU usage (`RLIMIT_CPU`)
+  - File sizes (`RLIMIT_FSIZE`)
+  - Number of open files, memory, etc. :contentReference[oaicite:7]{index=7}.
+- Helps contain rogue or misbehaving processes, essential for robustness.
+
+---
+
+## ✅ Why It Matters
+Advanced control over process scheduling, priorities, affinity, and resource limits is critical for writing:
+- Real-time or latency-sensitive applications
+- High-performance servers that benefit from core binding
+- Robust daemons that avoid resource exhaustion
+
+This chapter equips systems programmers with the tools to finely tune how tasks interact with the kernel scheduler and manage system impact.
+
+---
+
+## 📚 References
+- *Linux System Programming*, 2nd Ed. — Robert Love  
+- `man 2 sched_setscheduler`, `man 2 setrlimit`, `man 2 sched_getaffinity`  
+- Wikipedia: [Completely Fair Scheduler](https://en.wikipedia.org/wiki/Completely_Fair_Scheduler) :contentReference[oaicite:8]{index=8}
+

exercises/mycp/main.c

@@ -1,69 +1,71 @@
+#include <errno.h>
+#include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
-#include <fcntl.h>
-#include <errno.h>
 
 #define BUFF_LEN 4096
 
+int main(int argc, char *argv[])
+{
+	// Check number of arguments
+	if (argc < 3) {
+		fprintf(stderr, "Usage: %s SOURCE DEST\n", argv[0]);
+		return EXIT_FAILURE;
+	}
 
-int main(int argc, char *argv[]) {
-    // Check number of arguments
-    if (argc < 3) {
-        fprintf(stderr, "Usage: %s SOURCE DEST\n", argv[0]);
-        return EXIT_FAILURE;
-    }
+	// Get arguments
+	const char *src = argv[1];
+	const char *dst = argv[2];
 
-    // Get arguments
-    const char *src = argv[1];
-    const char *dst = argv[2];
+	// Open source file in read only mode
+	int srcfd = open(src, O_RDONLY);
+	if (srcfd == -1) {
+		perror("Failed open source file");
+		return EXIT_FAILURE;
+	}
 
-    // Open source file in read only mode
-    int srcfd = open(src, O_RDONLY);
-    if (srcfd == -1) {
-        perror("Failed open source file");
-        return EXIT_FAILURE;
-    }
-    
-    // Open destination file in write mode, if exists trunc file otherwise create a new file
-    int dstfd = open(dst, O_WRONLY | O_CREAT | O_TRUNC, 0644);
-    if (dstfd == -1) {
-        perror("Failed open destination file");
-        if (close(srcfd) == -1) {
-            perror("Failed close source file");
-        }
-        return EXIT_FAILURE;
-    } 
+	// Open destination file in write mode, if exists trunc file otherwise
+	// create a new file
+	int dstfd = open(dst, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+	if (dstfd == -1) {
+		perror("Failed open destination file");
+		if (close(srcfd) == -1) {
+			perror("Failed close source file");
+		}
+		return EXIT_FAILURE;
+	}
 
-    int exit_code = EXIT_SUCCESS;
-    char buff[BUFF_LEN];                // reading data buffer
-    ssize_t read_bytes;
-    while ((read_bytes = read(srcfd, buff, BUFF_LEN)) != 0) {
-        if (read_bytes == -1) {
-            // There is an error for reading source file
-            if (errno == EINTR) continue;
-            perror("Failed to read source file");
-            exit_code = EXIT_FAILURE;
-            break;
-        }
+	int exit_code = EXIT_SUCCESS;
+	char buff[BUFF_LEN]; // reading data buffer
+	ssize_t read_bytes;
+	while ((read_bytes = read(srcfd, buff, BUFF_LEN)) != 0) {
+		if (read_bytes == -1) {
+			// There is an error for reading source file
+			if (errno == EINTR)
+				continue;
+			perror("Failed to read source file");
+			exit_code = EXIT_FAILURE;
+			break;
+		}
 
-        // Write buffer at destination file
-        if (write(dstfd, buff, read_bytes) == -1) {
-            perror("Error to write to destination file");
-            exit_code = EXIT_FAILURE;
-            break;
-        }
-    }    
+		// Write buffer at destination file
+		if (write(dstfd, buff, read_bytes) == -1) {
+			perror("Error to write to destination file");
+			exit_code = EXIT_FAILURE;
+			break;
+		}
+	}
 
-    // Try to close files
-    if (close(srcfd) == -1) {
-        perror("Failed to close source file");
-        exit_code = EXIT_FAILURE;
-    }
-    if (close(dstfd) == -1) {
-        perror("Failed to close destination file");
-        exit_code = EXIT_FAILURE;
-    }
+	// Try to close files
+	if (close(srcfd) == -1) {
+		perror("Failed to close source file");
+		exit_code = EXIT_FAILURE;
+	}
+	if (close(dstfd) == -1) {
+		perror("Failed to close destination file");
+		exit_code = EXIT_FAILURE;
+	}
 
-    return exit_code;
+	return exit_code;
 }

exercises/tree/main.c

@@ -1,15 +1,15 @@
+#include "tree.h"
 #include <stdio.h>
 #include <stdlib.h>
-#include "tree.h"
 
-int main(int argc, char *argv[]) {
-    const char *path = (argc > 1) ? argv[1] : ".";
+int main(int argc, char *argv[])
+{
+	const char *path = (argc > 1) ? argv[1] : ".";
 
-    if (print_tree(path, 0) == -1) {
-        perror("Error traversing directory");
-        return EXIT_FAILURE;
-    }
+	if (print_tree(path, 0) == -1) {
+		perror("Error traversing directory");
+		return EXIT_FAILURE;
+	}
 
-    return EXIT_SUCCESS;
+	return EXIT_SUCCESS;
 }
-

exercises/tree/tree.c

@@ -1,35 +1,39 @@
+#include "tree.h"
+#include <dirent.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <dirent.h>
 #include <sys/stat.h>
 #include <unistd.h>
-#include "tree.h"
 
-int print_tree(const char *path, int depth) {
-    DIR *dir = opendir(path);
-    if (!dir) return -1;
+int print_tree(const char *path, int depth)
+{
+	DIR *dir = opendir(path);
+	if (!dir)
+		return -1;
 
-    struct dirent *entry;
-    while ((entry = readdir(dir)) != NULL) {
-        // Skip . and ..
-        if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
-            continue;
+	struct dirent *entry;
+	while ((entry = readdir(dir)) != NULL) {
+		// Skip . and ..
+		if (strcmp(entry->d_name, ".") == 0 ||
+		    strcmp(entry->d_name, "..") == 0)
+			continue;
 
-        for (int i = 0; i < depth; i++) printf("  ");
-        printf("|-- %s\n", entry->d_name);
+		for (int i = 0; i < depth; i++)
+			printf("  ");
+		printf("|-- %s\n", entry->d_name);
 
-        // Construct full path
-        char full_path[4096];
-        snprintf(full_path, sizeof(full_path), "%s/%s", path, entry->d_name);
+		// Construct full path
+		char full_path[4096];
+		snprintf(full_path, sizeof(full_path), "%s/%s", path,
+			 entry->d_name);
 
-        struct stat st;
-        if (stat(full_path, &st) == 0 && S_ISDIR(st.st_mode)) {
-            print_tree(full_path, depth + 1);
-        }
-    }
+		struct stat st;
+		if (stat(full_path, &st) == 0 && S_ISDIR(st.st_mode)) {
+			print_tree(full_path, depth + 1);
+		}
+	}
 
-    closedir(dir);
-    return 0;
+	closedir(dir);
+	return 0;
 }
-

exercises/tree/tree.h

@@ -4,4 +4,3 @@
 int print_tree(const char *path, int depth);
 
 #endif
-