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1 /* Save and restore the working directory, possibly using a subprocess. |
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2 |
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3 Copyright (C) 2006 Free Software Foundation, Inc. |
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4 |
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5 This program is free software; you can redistribute it and/or modify |
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6 it 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 This program is distributed in the hope that it will be useful, |
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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13 GNU 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 this program; if not, write to the Free Software Foundation, |
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17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ |
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18 |
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19 /* Written by Paul Eggert. */ |
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20 |
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21 #ifndef SAVEWD_H |
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22 # define SAVEWD_H 1 |
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23 |
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24 #include <stdbool.h> |
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25 #include <sys/types.h> |
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26 |
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27 /* A saved working directory. The member names and constants defined |
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28 by this structure are private to the savewd module. */ |
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29 struct savewd |
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30 { |
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31 /* The state of this object. */ |
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32 enum |
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33 { |
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34 /* This object has been created but does not yet represent |
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35 the working directory. */ |
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36 INITIAL_STATE, |
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37 |
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38 /* val.fd is the original working directory's file descriptor. |
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39 It is still the working directory. */ |
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40 FD_STATE, |
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41 |
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42 /* Like FD_STATE, but the working directory has changed, so |
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43 restoring it will require a fchdir. */ |
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44 FD_POST_CHDIR_STATE, |
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45 |
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46 /* Fork and let the subprocess do the work. val.child is 0 in a |
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47 child, negative in a childless parent, and the child process |
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48 ID in a parent with a child. */ |
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49 FORKING_STATE, |
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50 |
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51 /* A serious problem argues against further efforts. val.errnum |
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52 contains the error number (e.g., EIO). */ |
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53 ERROR_STATE, |
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54 |
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55 /* savewd_finish has been called, so the application no longer |
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56 cares whether the working directory is saved, and there is no |
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57 more work to do. */ |
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58 FINAL_STATE |
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59 } state; |
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60 |
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61 /* The object's value. */ |
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62 union |
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63 { |
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64 int fd; |
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65 int errnum; |
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66 pid_t child; |
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67 } val; |
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68 }; |
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69 |
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70 /* Initialize a saved working directory object. */ |
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71 static inline void |
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72 savewd_init (struct savewd *wd) |
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73 { |
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74 wd->state = INITIAL_STATE; |
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75 } |
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76 |
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77 |
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78 /* Options for savewd_chdir. */ |
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79 enum |
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80 { |
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81 /* Do not follow symbolic links, if supported. */ |
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82 SAVEWD_CHDIR_NOFOLLOW = 1, |
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83 |
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84 /* The directory should be readable, so fail if it happens to be |
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85 discovered that the directory is not readable. (Unreadable |
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86 directories are not necessarily diagnosed, though.) */ |
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87 SAVEWD_CHDIR_READABLE = 2, |
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88 |
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89 /* Do not chdir if the directory is readable; simply succeed |
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90 without invoking chdir if the directory was opened. */ |
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91 SAVEWD_CHDIR_SKIP_READABLE = 4 |
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92 }; |
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93 |
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94 /* Change the directory, and if successful, record into *WD the fact |
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95 that the process chdired into DIR. A process using this module |
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96 should use savewd_chdir rather than chdir or fchdir. Obey the |
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97 options specified in OPTIONS. |
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98 |
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99 If OPEN_RESULT is not null, store into OPEN_RESULT[0] a file |
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100 descriptor that accesses DIR if a file descriptor is successfully |
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101 obtained. Store -1 otherwise, setting OPEN_RESULT[1] to the error |
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102 number. Store through OPEN_RESULT regardless of whether the chdir |
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103 is successful. However, when -2 is returned, the contents of |
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104 OPEN_RESULT are indeterminate since the file descriptor is closed |
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105 in the parent. |
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106 |
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107 Return -2 if a subprocess was spun off to do the real work, -1 |
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108 (setting errno) if unsuccessful, 0 if successful. */ |
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109 int savewd_chdir (struct savewd *wd, char const *dir, int options, |
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110 int open_result[2]); |
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111 |
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112 /* Restore the working directory from *WD. STATUS indicates the exit |
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113 status corresponding to the work done since the last save; this is |
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114 used when the caller is in a subprocess. Return 0 if successful, |
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115 -1 (setting errno) on our failure, a positive subprocess exit |
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116 status if the working directory was restored in the parent but the |
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117 subprocess failed. */ |
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118 int savewd_restore (struct savewd *wd, int status); |
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119 |
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120 /* Return WD's error number, or 0 if WD is not in an error state. */ |
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121 static inline int |
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122 savewd_errno (struct savewd const *wd) |
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123 { |
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124 return (wd->state == ERROR_STATE ? wd->val.errnum : 0); |
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125 } |
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126 |
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127 /* Deallocate any resources associated with WD. A program that chdirs |
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128 should restore before finishing. */ |
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129 void savewd_finish (struct savewd *wd); |
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130 |
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131 /* Process N_FILES file names, FILE[0] through FILE[N_FILES - 1]. |
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132 For each file name F, call ACT (F, WD, OPTIONS); ACT should invoke |
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133 savewd_chdir as needed, and should return an exit status. WD |
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134 represents the working directory; it may be in an error state when |
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135 ACT is called. |
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136 |
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137 Save and restore the working directory as needed by the file name |
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138 vector; assume that ACT does not require access to any relative |
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139 file names other than its first argument, and that it is OK if the |
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140 working directory is changed when this function returns. Some |
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141 actions may be applied in a subprocess. |
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142 |
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143 Return the maximum exit status that any call to ACT returned, or |
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144 EXIT_SUCCESS (i.e., 0) if no calls were made. */ |
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145 int savewd_process_files (int n_files, char **file, |
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146 int (*act) (char *, struct savewd *, void *), |
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147 void *options); |
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148 |
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149 #endif |
