Change the access permissions of a file or directory. More information: <https://www.gnu.org/software/coreutils/chmod>.

• Give the [u]ser who owns a file the right to e[x]ecute it:
  chmod u+x path/to/file
• Give the [u]ser rights to [r]ead and [w]rite to a file/directory:
  chmod u+rw path/to/file_or_directory
• Remove e[x]ecutable rights from the [g]roup:
  chmod g-x path/to/file
• Give [a]ll users rights to [r]ead and e[x]ecute:
  chmod a+rx path/to/file
• Give [o]thers (not in the file owner's group) the same rights as the [g]roup:
  chmod o=g path/to/file
• Remove all rights from [o]thers:
  chmod o= path/to/file
• Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:
  chmod -R g+w,o+w path/to/directory
• Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:
  chmod -R a+rX path/to/directory

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