1 | /* |
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2 | FUNCTION |
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3 | <<system>>---execute command string |
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4 | |
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5 | INDEX |
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6 | system |
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7 | INDEX |
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8 | _system_r |
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9 | |
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10 | SYNOPSIS |
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11 | #include <stdlib.h> |
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12 | int system(char *<[s]>); |
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13 | |
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14 | int _system_r(void *<[reent]>, char *<[s]>); |
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15 | |
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16 | DESCRIPTION |
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17 | |
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18 | Use <<system>> to pass a command string <<*<[s]>>> to <</bin/sh>> on |
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19 | your system, and wait for it to finish executing. |
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20 | |
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21 | Use ``<<system(NULL)>>'' to test whether your system has <</bin/sh>> |
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22 | available. |
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23 | |
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24 | The alternate function <<_system_r>> is a reentrant version. The |
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25 | extra argument <[reent]> is a pointer to a reentrancy structure. |
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26 | |
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27 | RETURNS |
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28 | <<system(NULL)>> returns a non-zero value if <</bin/sh>> is available, and |
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29 | <<0>> if it is not. |
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30 | |
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31 | With a command argument, the result of <<system>> is the exit status |
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32 | returned by <</bin/sh>>. |
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33 | |
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34 | PORTABILITY |
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35 | ANSI C requires <<system>>, but leaves the nature and effects of a |
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36 | command processor undefined. ANSI C does, however, specify that |
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37 | <<system(NULL)>> return zero or nonzero to report on the existence of |
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38 | a command processor. |
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39 | |
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40 | POSIX.2 requires <<system>>, and requires that it invoke a <<sh>>. |
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41 | Where <<sh>> is found is left unspecified. |
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42 | |
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43 | Supporting OS subroutines required: <<_exit>>, <<_execve>>, <<_fork_r>>, |
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44 | <<_wait_r>>. |
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45 | */ |
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46 | |
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47 | #include <_ansi.h> |
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48 | #include <errno.h> |
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49 | #include <stddef.h> |
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50 | #include <stdlib.h> |
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51 | #include <unistd.h> |
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52 | #include <_syslist.h> |
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53 | #include <reent.h> |
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54 | |
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55 | #if defined (unix) || defined (__CYGWIN__) |
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56 | static int do_system (struct _reent *ptr, const char *s); |
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57 | #endif |
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58 | |
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59 | int |
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60 | _system_r (struct _reent *ptr, |
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61 | const char *s) |
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62 | { |
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63 | #if defined(HAVE_SYSTEM) |
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64 | return _system (s); |
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65 | ptr = ptr; |
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66 | #elif defined(NO_EXEC) |
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67 | if (s == NULL) |
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68 | return 0; |
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69 | errno = ENOSYS; |
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70 | return -1; |
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71 | #else |
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72 | |
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73 | /* ??? How to handle (s == NULL) here is not exactly clear. |
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74 | If _fork_r fails, that's not really a justification for returning 0. |
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75 | For now we always return 0 and leave it to each target to explicitly |
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76 | handle otherwise (this can always be relaxed in the future). */ |
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77 | |
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78 | #if defined (unix) || defined (__CYGWIN__) |
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79 | if (s == NULL) |
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80 | return 1; |
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81 | return do_system (ptr, s); |
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82 | #else |
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83 | if (s == NULL) |
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84 | return 0; |
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85 | errno = ENOSYS; |
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86 | return -1; |
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87 | #endif |
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88 | |
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89 | #endif |
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90 | } |
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91 | |
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92 | #ifndef _REENT_ONLY |
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93 | |
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94 | int |
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95 | system (const char *s) |
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96 | { |
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97 | return _system_r (_REENT, s); |
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98 | } |
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99 | |
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100 | #endif |
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101 | |
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102 | #if defined (unix) && !defined (__CYGWIN__) && !defined(__rtems__) |
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103 | extern char **environ; |
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104 | |
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105 | /* Only deal with a pointer to environ, to work around subtle bugs with shared |
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106 | libraries and/or small data systems where the user declares his own |
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107 | 'environ'. */ |
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108 | static char ***p_environ = &environ; |
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109 | |
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110 | static int |
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111 | do_system (struct _reent *ptr, |
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112 | const char *s) |
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113 | { |
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114 | char *argv[4]; |
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115 | int pid, status; |
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116 | |
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117 | argv[0] = "sh"; |
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118 | argv[1] = "-c"; |
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119 | argv[2] = (char *) s; |
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120 | argv[3] = NULL; |
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121 | |
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122 | if ((pid = _fork_r (ptr)) == 0) |
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123 | { |
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124 | _execve ("/bin/sh", argv, *p_environ); |
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125 | exit (100); |
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126 | } |
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127 | else if (pid == -1) |
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128 | return -1; |
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129 | else |
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130 | { |
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131 | int rc = _wait_r (ptr, &status); |
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132 | if (rc == -1) |
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133 | return -1; |
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134 | status = (status >> 8) & 0xff; |
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135 | return status; |
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136 | } |
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137 | } |
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138 | #endif |
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139 | |
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140 | #if defined (__CYGWIN__) |
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141 | static int |
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142 | do_system (struct _reent *ptr, |
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143 | const char *s) |
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144 | { |
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145 | char *argv[4]; |
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146 | int pid, status; |
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147 | |
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148 | argv[0] = "sh"; |
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149 | argv[1] = "-c"; |
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150 | argv[2] = (char *) s; |
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151 | argv[3] = NULL; |
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152 | |
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153 | if ((pid = vfork ()) == 0) |
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154 | { |
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155 | /* ??? It's not clear what's the right path to take (pun intended :-). |
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156 | There won't be an "sh" in any fixed location so we need each user |
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157 | to be able to say where to find "sh". That suggests using an |
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158 | environment variable, but after a few more such situations we may |
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159 | have too many of them. */ |
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160 | char *sh = getenv ("SH_PATH"); |
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161 | if (sh == NULL) |
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162 | sh = "/bin/sh"; |
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163 | _execve (sh, argv, environ); |
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164 | exit (100); |
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165 | } |
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166 | else if (pid == -1) |
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167 | return -1; |
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168 | else |
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169 | { |
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170 | extern int _wait (int *); |
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171 | int rc = _wait (&status); |
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172 | if (rc == -1) |
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173 | return -1; |
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174 | status = (status >> 8) & 0xff; |
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175 | return status; |
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176 | } |
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177 | } |
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178 | #endif |
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