{"id":8557,"date":"2013-06-23T19:41:19","date_gmt":"2013-06-23T19:41:19","guid":{"rendered":"http:\/\/www.beautifulwork.org\/?page_id=8557"},"modified":"2013-06-23T19:41:19","modified_gmt":"2013-06-23T19:41:19","slug":"true-and-false-notes","status":"publish","type":"post","link":"https:\/\/www.trueangle.org\/index.php\/2013\/06\/23\/true-and-false-notes\/","title":{"rendered":"true and false notes"},"content":{"rendered":"\n\n\n\n
\n

A UNIX Command <\/u><\/h2>\n
\n$true\n$echo $?\n0\n$false\n$echo $?\n1\n$\n\n$ .\/true --version >&-\n.\/true: write error: Bad file number\n$ .\/true --version > \/dev\/full\n.\/true: write error: No space left on device\n\n\n<\/pre>\n<\/td>\n

\n

UNIX Explanation<\/u><\/h2>\n
\ntrue - do nothing, successfully\nexit with a status code indicating success.\nfalse - do nothing, unsuccessfully\nexit with a status code indicating failure.\n<\/pre>\n<\/td>\n<\/tr>\n

\n

Related Source Code Exposition<\/u><\/h2>\n
\nint\nmain (int argc, char **argv)\n{\n\n  if (argc == 2)\n    {\n      initialize_main (&argc, &argv);\n      set_program_name (argv[0]);\n      setlocale (LC_ALL, \"\");\n      bindtextdomain (PACKAGE, LOCALEDIR);\n      textdomain (PACKAGE);\n\n      atexit (close_stdout);\n\n      if (STREQ (argv[1], \"--help\"))\n        usage (EXIT_STATUS);\n\n      if (STREQ (argv[1], \"--version\"))\n        version_etc (stdout, PROGRAM_NAME, PACKAGE_NAME, Version, AUTHORS,\n                     (char *) NULL);\n    }\n\n  exit (EXIT_STATUS);\n}\n <\/pre>\n<\/td>\n

\n

Source Code Highlight<\/u><\/h2>\n
\nRecognize --help or --version only if it's the only\ncommand-line argument.\n<\/pre>\n<\/td>\n<\/tr>\n

\n

Featured Image <\/u><\/h2>\n

\"\"<\/a>\n<\/td>\n

\n

Related Knowledge <\/u><\/h2>\n
\n`true' does  nothing except return  an exit status  of 0,\nmeaning \"success\".  It  can be used as a  place holder in\nshell  scripts  where  a  successful command  is  needed,\nalthough the  shell built-in  command `:' (colon)  may do\nthe same thing faster.   In most modern shells, `true' is\na built-in command,  so when you use `true'  in a script,\nyou're probably  using the built-in command,  not the one\ndocumented here.\n\n<\/pre>\n
\nNote,  however, that it  is possible  to cause  `true' to\nexit   with  nonzero   status:  with   the   `--help'  or\n`--version'  option,  and  with standard  output  already\nclosed or redirected to a  file that evokes an I\/O error.\nFor example, using a Bourne-compatible shell:\n\n<\/pre>\n
\nThis version of `true' is implemented as a C program, and\nis  thus  more secure  and  faster  than  a shell  script\nimplementation, and  may safely be used as  a dummy shell\nfor the purpose of disabling accounts.\n\n<\/pre>\n
source : info coreutils ‘true invocation’<\/p>\n

\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":"

A UNIX Command $true $echo $? 0 $false $echo $? 1 $ $ .\/true –version >&- .\/true: write error: Bad file number $ .\/true –version > \/dev\/full .\/true: write error: No space left on device UNIX Explanation true – do nothing, successfully exit with a status code indicating success. false – do nothing, unsuccessfully exit … <\/p>\n

Continue reading “true and false notes”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"page-templates\/full-width.php","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/posts\/8557"}],"collection":[{"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/comments?post=8557"}],"version-history":[{"count":0,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/posts\/8557\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/media?parent=8557"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/categories?post=8557"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.trueangle.org\/index.php\/wp-json\/wp\/v2\/tags?post=8557"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}