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Process A Process B
kill
Process A Process B
kill
Run default signal handler!
kill Run default signal handler! Process Process A B kill - - PowerPoint PPT Presentation
kill Run default signal handler! Process Process A B kill - - PowerPoint PPT Presentation
Process Process A B kill Run default signal handler! Process Process A B kill signal(SIGINT, func) Process Process A B signal(SIGINT, func) Process Process A B kill Run fun signal handler! Terminate process Generate Core
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Process A Process B
signal(SIGINT, func)
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Process A Process B
signal(SIGINT, func) kill
Run fun signal handler!
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Terminate process Generate Core Dump Ignore Stop
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void sigint_handler(int sig) { char c; signal(sig, SIG_IGN); printf(Ouch, you just hit Ctrl-C?. Do you really want to quit [y/n]?); c = getchar(); if (c == y || c = Y) exit(0); else signal(SIGINT, sigint_handler); }
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int main(int argc, char **argv) { int pid, status; int newfd; if ((newfd = open("output_file.txt", O_CREAT|O_TRUNC|O_WRONLY, 0644)) < 0) { exit(1); } printf("Luke, I am your..."); dup2(newfd, 1); printf("father"); exit(0); }
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int main(int argc, char **argv) { int pid, status; int newfd; char *cmd[] = { "/bin/ls", "-al", "/", 0 }; if (argc != 2) { fprintf(stderr, "usage: %s output_file\n", argv[0]); exit(1); } if ((newfd = open(argv[1], O_CREAT|O_TRUNC|O_WRONLY, 0644)) < 0) { perror(argv[1]); /* open failed */ exit(1); } printf("writing output of the command %s to \"%s\"\n", cmd[0], argv[1]); dup2(newfd, 1); execvp(cmd[0], cmd); perror(cmd[0]); /* execvp failed */ exit(1); }
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int fd = open(“hello.txt”, FLAGS)
a b c d e f g h j k l m
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read(fd, buffer, 2)
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read(fd, buffer, 2)
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ab
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write(fd, “12”, 2)
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write(fd, “12”, 2)
a b 1 2 e f g h j k l m
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lseek(fd, 2, SEEK_CUR)
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lseek(fd, 2, SEEK_CUR)
a b 1 2 e f g h j k l m
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lseek(fd, 10, SEEK_END)
a b 1 2 e f g h j k l m
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lseek(fd, 10, SEEK_END)
a b 1 2 e f g h j k l m
note that we don’t write \0 in the middle until we make a write
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write(fd, “lo”, 2)
a b 1 2 e f g h j k l m \0 \0 \0 \0 \0 \0 \0 \0 \0 \0 l
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Files Vs File Descriptor
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file descriptors
FD 1 2 Process B stdin stdout stderr a.txt b.txt Kernel File Table Process File Table
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- pen(“b.txt”, O_CREAT|O_WR)
FD 1 2 Process B 3 stdin stdout stderr a.txt b.txt Kernel File Table Process File Table
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dup(2)
FD 1 2 Process B 3 stdin stdout stderr a.txt b.txt Kernel File Table Process File Table 4
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dup2(3, STDOUT_FD)
FD 1 2 Process B 3 stdin stdout stderr a.txt b.txt Kernel File Table Process File Table 4