1p2open(3GEN)       String Pattern-Matching Library Functions      p2open(3GEN)
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NAME

6       p2open, p2close - open, close pipes to and from a command
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SYNOPSIS

9       cc [ flag ... ] file ... -lgen [ library ... ]
10       #include <libgen.h>
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12       int p2open(const char *cmd, FILE *fp[2]);
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15       int p2close(FILE *fp[2]);
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DESCRIPTION

19       The  p2open()gfunction forks and execs a shell running the command line
20       pointed to by cmd. On return, fp[0] points to a FILE pointer  to  write
21       the command's standard input and fp[1] points to a FILE pointer to read
22       from the command's  standard output.  In this way the program has  con‐
23       trol over the input and output of the command.
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26       The function returns 0 if successful; otherwise, it returns −1.
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29       The p2close() function is used to close the file pointers that p2open()
30       opened.  It waits for the process to terminate and returns the  process
31       status. It returns 0 if successful; otherwise, it returns −1.
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RETURN VALUES

34       A  common  problem  is  having  too few file descriptors. The p2close()
35       function returns −1 if the two file pointers  are  not  from  the  same
36       p2open().
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EXAMPLES

39       Example 1 Example of file descriptors.
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41         #include <stdio.h>
42         #include <libgen.h>
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44         main(argc,argv)
45         int argc;
46         char **argv;
47         {
48              FILE *fp[2];
49              pid_t pid;
50              char buf[16];
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52                 pid=p2open("/usr/bin/cat", fp);
53                 if ( pid == −1 ) {
54                   fprintf(stderr, "p2open failed\n");
55                   exit(1);
56              }
57              write(fileno(fp[0]),"This is a test\n", 16);
58              if(read(fileno(fp[1]), buf, 16) <=0)
59                   fprintf(stderr, "p2open failed\n");
60              else
61                   write(1, buf, 16);
62              (void)p2close(fp);
63         }
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ATTRIBUTES

67       See attributes(5) for descriptions of the following attributes:
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72       ┌─────────────────────────────┬─────────────────────────────┐
73       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
74       ├─────────────────────────────┼─────────────────────────────┤
75       │MT-Level                     │Unsafe                       │
76       └─────────────────────────────┴─────────────────────────────┘
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SEE ALSO

79       fclose(3C), popen(3C), setbuf(3C), attributes(5)
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NOTES

82       Buffered  writes  on  fp[0]  can make it appear that the command is not
83       listening. Judiciously placed fflush() calls or unbuffering  fp[0]  can
84       be a big help; see fclose(3C).
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87       Many  commands use buffered output when connected to a pipe. That, too,
88       can make it appear as if things are not working.
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91       Usage is not the same as for popen(), although it is closely related.
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95SunOS 5.11                        29 Dec 1996                     p2open(3GEN)
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