270 lines
7.0 KiB
C
270 lines
7.0 KiB
C
/* extcmd.c
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*
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* A test program to run an external command and capture its
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* stdout and stderr and exit code into varaibles to print later.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <fcntl.h>
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#include <sys/select.h>
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#include <sys/types.h>
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#include <signal.h>
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#include "extcmd.h"
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/* Takes a file descriptor and makes it non-blocking.
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*/
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static int
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set_nonblock(int fd)
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{
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int val;
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if((val = fcntl(fd, F_GETFL, 0)) < 0)
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{
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perror("fcntl F_GETFL error:");
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return(-1);
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}
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val |= O_NONBLOCK;
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if(fcntl(fd, F_SETFL, val) < 0)
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{
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perror("fcntl F_SETFL error setting O_NONBLOCK");
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return(-1);
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}
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return(0);
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}
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/* Run en external command returning exit status, and filling provided
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* buffers with STDOUT an STDERR up to the size provided.
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*/
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int
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run_extcmd(char *cmd, char *so_buf, char *se_buf, size_t so_buf_sz, size_t se_buf_sz, int *status)
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{
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//--DSS temp
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//return(0);
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pid_t pid;
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struct timeval tv;
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fd_set rfds;
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fd_set efds;
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int selval;
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int so[2], se[2]; /* For our pipes */
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int bytes_read;
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char so_read_buf[IO_READ_BUF_LEN];
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char se_read_buf[IO_READ_BUF_LEN];
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/* Set our remaining_buf counters to one less than the given size so we
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* can leave room for a terminating '\0'.
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*/
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int so_buf_remaining = (so_buf_sz > 0) ? so_buf_sz-1 : 0;
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int se_buf_remaining = (se_buf_sz > 0) ? se_buf_sz-1 : 0;
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/* Be optimistic :)
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*/
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int retval = EXTCMD_SUCCESS_ALL_OUTPUT;
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/* Create the pipes we will use for getting stdout and stderr
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* from the child process.
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*/
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pipe(so);
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pipe(se);
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/* Fork off a child process to run the command and provide its outputs.
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*/
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pid = fork();
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if(pid == -1)
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{
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return(EXTCMD_FORK_ERROR);
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}
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else if (pid == 0)
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{
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/* We are the child, so we dup stdout and stderr to our respective
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* write-end of the pipes, close stdin and the read-end of the pipes
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* (since we don't need them here). Then use system() to run the
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* command and exit with the exit status of that command so we can
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* grab it from the waitpid call in the parent.
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*/
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close(fileno(stdin));
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dup2(so[1], fileno(stdout));
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dup2(se[1], fileno(stderr));
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close(so[0]);
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close(se[0]);
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/* --DSS XXX: It would be more efficient to use one of the exec()
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* calls. (i.e. 'return(execvp(ext_cmd, &argv[1]));' ).
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* but for now, we use system() and exit with the external
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* command exit status.
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*/
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exit(WEXITSTATUS(system(cmd)));
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}
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/* Parent from here */
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/* Give the exit status an initial value of -1.
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*/
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*status = -1;
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/* Close the write-end of the pipes (we are only reading).
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*/
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close(so[1]);
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close(se[1]);
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/* Set our pipes to non-blocking
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*/
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set_nonblock(so[0]);
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set_nonblock(se[0]);
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tv.tv_sec = EXTCMD_DEF_TIMEOUT;
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tv.tv_usec = 0;
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/* Initialize and setup our file descriptor sets for select.
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*/
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FD_ZERO(&rfds);
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FD_ZERO(&efds);
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FD_SET(so[0], &rfds);
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FD_SET(se[0], &rfds);
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FD_SET(so[0], &efds);
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FD_SET(se[0], &efds);
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/* Start with fully clear buffers.
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*/
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memset(so_buf, 0x0, so_buf_sz);
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memset(se_buf, 0x0, se_buf_sz);
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/* Read both stdout and stderr piped from the child until we get eof,
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* fill the buffers, or error out.
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*/
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while(so_buf_remaining > 0 || se_buf_remaining > 0)
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{
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selval = select(8, &rfds, NULL, &efds, &tv);
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if(selval == -1)
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{
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/* Select error - so kill the child and bail.
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*/
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kill(pid, SIGTERM);
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retval |= EXTCMD_SELECT_ERROR;
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break;
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}
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if(selval == 0)
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{
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/* Timeout - so kill the child and bail
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*/
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kill(pid, SIGTERM);
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retval |= EXTCMD_EXECUTION_TIMEOUT;
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break;
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}
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/* The stdout pipe...
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*/
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bytes_read = read(so[0], so_read_buf, IO_READ_BUF_LEN);
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if(so_buf_remaining > 0)
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{
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if(bytes_read > 0)
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{
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/* We have data, so process it...
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*/
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if(bytes_read > so_buf_remaining)
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{
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bytes_read = so_buf_remaining;
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retval |= EXTCMD_SUCCESS_PARTIAL_STDOUT;
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}
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memcpy(so_buf, so_read_buf, bytes_read);
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so_buf += bytes_read;
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so_buf_remaining -= bytes_read;
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}
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else if(bytes_read < 0)
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{
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/* Anything other than EAGAIN or EWOULDBLOCK is conisdered
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* error enough to bail. We are done here so we force the
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* buf_remaining value to 0.
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*/
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if(errno != EAGAIN && errno != EWOULDBLOCK)
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{
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retval |= EXTCMD_STDOUT_READ_ERROR;
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so_buf_remaining = 0;
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}
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}
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else
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{
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/* Bytes read was 0 which indicate end of file. So we are
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* done.
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*/
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so_buf_remaining = 0;
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}
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}
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else
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break;
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/* The stderr pipe...
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*/
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bytes_read = read(se[0], se_read_buf, IO_READ_BUF_LEN);
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if(se_buf_remaining > 0)
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{
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if(bytes_read > 0)
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{
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/* We have data, so process it...
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*/
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if(bytes_read > se_buf_remaining)
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{
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bytes_read = se_buf_remaining;
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retval |= EXTCMD_SUCCESS_PARTIAL_STDERR;
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}
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memcpy(se_buf, se_read_buf, bytes_read);
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se_buf += bytes_read;
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se_buf_remaining -= bytes_read;
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}
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else if(bytes_read < 0)
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{
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/* Anything other than EAGAIN or EWOULDBLOCK is conisdered
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* error enough to bail. We are done here so we force the
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* buf_remaining value to 0.
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*/
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if(errno != EAGAIN && errno != EWOULDBLOCK)
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{
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retval |= EXTCMD_STDERR_READ_ERROR;
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se_buf_remaining = 0;
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}
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}
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else
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{
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/* Bytes read was 0 which indicate end of file. So we are
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* done.
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*/
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se_buf_remaining = 0;
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}
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}
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else
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break;
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}
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close(so[0]);
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close(se[0]);
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/* Wait for the external command to finish and capture its exit status.
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*/
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waitpid(pid, status, 0);
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if(*status != 0)
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retval != EXTCMD_EXECUTION_ERROR;
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/* Return the our status of this operation command.
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*/
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return(retval);
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}
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