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1 ## Copyright (C) 1996, 1997 John W. Eaton |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 2, or (at your option) |
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8 ## any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, write to the Free |
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17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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18 ## 02110-1301, USA. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {[@var{in}, @var{out}, @var{pid}] =} popen2 (@var{command}, @var{args}) |
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22 ## Start a subprocess with two-way communication. The name of the process |
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23 ## is given by @var{command}, and @var{args} is an array of strings |
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24 ## containing options for the command. The file identifiers for the input |
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25 ## and output streams of the subprocess are returned in @var{in} and |
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26 ## @var{out}. If execution of the command is successful, @var{pid} |
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27 ## contains the process ID of the subprocess. Otherwise, @var{pid} is |
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28 ## @minus{}1. |
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29 ## |
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30 ## For example, |
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31 ## |
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32 ## @example |
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33 ## @group |
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34 ## [in, out, pid] = popen2 ("sort", "-nr"); |
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35 ## fputs (in, "these\nare\nsome\nstrings\n"); |
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36 ## fclose (in); |
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37 ## EAGAIN = errno ("EAGAIN"); |
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38 ## done = false; |
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39 ## do |
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40 ## s = fgets (out); |
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41 ## if (ischar (s)) |
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42 ## fputs (stdout, s); |
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43 ## elseif (errno () == EAGAIN) |
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44 ## sleep (0.1); |
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45 ## fclear (out); |
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46 ## else |
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47 ## done = true; |
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48 ## endif |
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49 ## until (done) |
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50 ## fclose (out); |
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51 ## @print{} are |
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52 ## @print{} some |
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53 ## @print{} strings |
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54 ## @print{} these |
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55 ## @end group |
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56 ## @end example |
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57 ## @end deftypefn |
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58 |
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59 ## Author: jwe |
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60 |
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61 function [in, out, pid] = popen2 (command, args) |
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62 |
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63 in = -1; |
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64 out = -1; |
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65 pid = -1; |
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66 |
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67 if (nargin == 1 || nargin == 2) |
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68 |
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69 if (nargin == 1) |
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70 args = ""; |
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71 endif |
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72 |
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73 if (ischar (command)) |
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74 |
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75 [stdin_pipe, stdin_status] = pipe (); |
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76 [stdout_pipe, stdout_status] = pipe (); |
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77 |
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78 if (stdin_status == 0 && stdout_status == 0) |
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79 |
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80 pid = fork (); |
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81 |
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82 if (pid == 0) |
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83 |
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84 ## In the child. |
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85 |
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86 fclose (nth (stdin_pipe, 2)); |
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87 fclose (nth (stdout_pipe, 1)); |
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88 |
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89 dup2 (nth (stdin_pipe, 1), stdin); |
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90 fclose (nth (stdin_pipe, 1)); |
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91 |
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92 dup2 (nth (stdout_pipe, 2), stdout); |
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93 fclose (nth (stdout_pipe, 2)); |
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94 |
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95 if (exec (command, args) < 0) |
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96 error ("popen2: unable to start process `%s'", command); |
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97 exit (0); |
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98 endif |
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99 |
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100 elseif (pid) |
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101 |
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102 ## In the parent. |
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103 |
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104 fclose (nth (stdin_pipe, 1)); |
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105 fclose (nth (stdout_pipe, 2)); |
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106 |
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107 if (fcntl (nth (stdout_pipe, 1), F_SETFL, O_NONBLOCK) < 0) |
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108 error ("popen2: error setting file mode"); |
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109 else |
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110 in = nth (stdin_pipe, 2); |
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111 out = nth (stdout_pipe, 1); |
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112 endif |
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113 |
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114 elseif (pid < 0) |
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115 error ("popen2: fork failed -- unable to create child process"); |
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116 endif |
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117 else |
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118 error ("popen2: pipe creation failed"); |
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119 endif |
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120 else |
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121 error ("popen2: file name must be a string"); |
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122 endif |
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123 else |
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124 usage ("[in, out, pid] = popen2 (command, args)"); |
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125 endif |
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126 |
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127 endfunction |
