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readonly.1p (4603B)

    

  1. '\" et
  2. .TH READONLY "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
  3. .\"
  4. .SH PROLOG
  5. This manual page is part of the POSIX Programmer's Manual.
  6. The Linux implementation of this interface may differ (consult
  7. the corresponding Linux manual page for details of Linux behavior),
  8. or the interface may not be implemented on Linux.
  9. .\"
  10. .SH NAME
  11. readonly
  12. \(em set the readonly attribute for variables
  13. .SH SYNOPSIS
  14. .LP
  15. .nf
  16. readonly name\fB[\fR=\fIword\fB]\fR...
  17. .P
  18. readonly\fR -p
  19. .fi
  20. .SH DESCRIPTION
  21. The variables whose
  22. .IR name s
  23. are specified shall be given the
  24. .IR readonly
  25. attribute. The values of variables with the
  26. .IR readonly
  27. attribute cannot be changed by subsequent assignment, nor can those
  28. variables be unset by the
  29. .IR unset
  30. utility. If the name of a variable is followed by =\c
  31. .IR word ,
  32. then the value of that variable shall be set to
  33. .IR word .
  34. .P
  35. The
  36. .IR readonly
  37. special built-in shall support the Base Definitions volume of POSIX.1\(hy2017,
  38. .IR "Section 12.2" ", " "Utility Syntax Guidelines".
  39. .P
  40. When
  41. .BR \-p
  42. is specified,
  43. .IR readonly
  44. writes to the standard output the names and values of all read-only
  45. variables, in the following format:
  46. .sp
  47. .RS 4
  48. .nf
  50. "readonly %s=%s\en", <\fIname\fR>, <\fIvalue\fR>
  51. .fi
  52. .P
  53. .RE
  54. .P
  55. if
  56. .IR name
  57. is set, and
  58. .sp
  59. .RS 4
  60. .nf
  62. "readonly %s\en", <\fIname\fR>
  63. .fi
  64. .P
  65. .RE
  66. .P
  67. if
  68. .IR name
  69. is unset.
  70. .P
  71. The shell shall format the output, including the proper use of quoting,
  72. so that it is suitable for reinput to the shell as commands that
  73. achieve the same value and
  74. .IR readonly
  75. attribute-setting results in a shell execution environment in which:
  76. .IP " 1." 4
  77. Variables with values at the time they were output do not have the
  78. .IR readonly
  79. attribute set.
  80. .IP " 2." 4
  81. Variables that were unset at the time they were output do not have a
  82. value at the time at which the saved output is reinput to the shell.
  83. .P
  84. When no arguments are given, the results are unspecified.
  85. .SH OPTIONS
  86. See the DESCRIPTION.
  87. .SH OPERANDS
  88. See the DESCRIPTION.
  89. .SH STDIN
  90. Not used.
  91. .SH "INPUT FILES"
  92. None.
  93. .SH "ENVIRONMENT VARIABLES"
  94. None.
  95. .SH "ASYNCHRONOUS EVENTS"
  96. Default.
  97. .SH STDOUT
  98. See the DESCRIPTION.
  99. .SH STDERR
  100. The standard error shall be used only for diagnostic messages.
  101. .SH "OUTPUT FILES"
  102. None.
  103. .SH "EXTENDED DESCRIPTION"
  104. None.
  105. .SH "EXIT STATUS"
  106. .IP "\00" 6
  107. All
  108. .IR name
  109. operands were successfully marked readonly.
  110. .IP >0 6
  111. At least one
  112. .IR name
  113. could not be marked readonly, or the
  114. .BR \-p
  115. option was specified and an error occurred.
  116. .SH "CONSEQUENCES OF ERRORS"
  117. Default.
  118. .LP
  119. .IR "The following sections are informative."
  120. .SH "APPLICATION USAGE"
  121. None.
  122. .SH EXAMPLES
  123. .LP
  124. .nf
  125. readonly HOME PWD
  126. .fi
  127. .SH "RATIONALE"
  128. Some historical shells preserve the
  129. .IR readonly
  130. attribute across separate invocations. This volume of POSIX.1\(hy2017 allows this behavior,
  131. but does not require it.
  132. .P
  133. The
  134. .BR \-p
  135. option allows portable access to the values that can be saved and then
  136. later restored using, for example, a
  137. .IR dot
  138. script. Also see the RATIONALE for
  139. .IR "\fIexport\fR\^"
  140. for a description of the no-argument and
  141. .BR \-p
  142. output cases and a related example.
  143. .P
  144. Read-only functions were considered, but they were omitted as not being
  145. historical practice or particularly useful. Furthermore, functions must
  146. not be read-only across invocations to preclude ``spoofing''
  147. (spoofing is the term for the practice of creating a program that acts
  148. like a well-known utility with the intent of subverting the real intent
  149. of the user) of administrative or security-relevant (or
  150. security-conscious) shell scripts.
  151. .SH "FUTURE DIRECTIONS"
  152. None.
  153. .SH "SEE ALSO"
  154. .IR "Section 2.14" ", " "Special Built-In Utilities"
  155. .P
  156. The Base Definitions volume of POSIX.1\(hy2017,
  157. .IR "Section 12.2" ", " "Utility Syntax Guidelines"
  158. .\"
  159. .SH COPYRIGHT
  160. Portions of this text are reprinted and reproduced in electronic form
  161. from IEEE Std 1003.1-2017, Standard for Information Technology
  162. -- Portable Operating System Interface (POSIX), The Open Group Base
  163. Specifications Issue 7, 2018 Edition,
  164. Copyright (C) 2018 by the Institute of
  165. Electrical and Electronics Engineers, Inc and The Open Group.
  166. In the event of any discrepancy between this version and the original IEEE and
  167. The Open Group Standard, the original IEEE and The Open Group Standard
  168. is the referee document. The original Standard can be obtained online at
  169. http://www.opengroup.org/unix/online.html .
  170. .PP
  171. Any typographical or formatting errors that appear
  172. in this page are most likely
  173. to have been introduced during the conversion of the source files to
  174. man page format. To report such errors, see
  175. https://www.kernel.org/doc/man-pages/reporting_bugs.html .