ctools - core tools
*ctools* provides the *core tools* of a POSIX-1.2017-compatible operating
system, with optional XSI support. These tools provide the core utilities
necessary for a useful scripting environment and a comfortable interactive
shell environment. These tools are used for tasks such as:
- Manipulating and examining the filesystem
- Operations on text files, strings, and paths
- Managing processes on the system
*ctools* provides the following tools:
:< Print the filename part of a pathname
: Concatenate files
: Change group ownership of files
: Change the mode of files
: Change ownership of files
: Calculate the cyclic redundancy check (CRC) for files
: Compare two files
: Compare two sorted files
: Print the directory part of a pathname
: Writes arguments to the standard output
: Run command with a specified environment
: Exit with status code 1
: Print the beginning of files
: Create a hard link
: Print the name of the login user
: Invoke a command that ignores hangups
: Run a process with an altered niceness value
: Remove directories
: Suspend execution for an interval
: Duplicate standard input
: Exit with status code 0
: Print the name of the controlling tty
: Print the name(s) of the system
: Unlink a file
Detailed information about each tool is available in its respective manual.
# COMMON BEHAVIORS
Most commands adhere to a few common conventions, which are explained here and
only mentioned in each utility's manual if its behavior differs from these
## UTILITY SYNTAX
Most tools conform to the XBD Utility Syntax Guidelines. Their usage takes the
*command* [-options...] [--] [_argument_...]
In the manual, [ ] is used to indicate optional parameters, and ... is used to
indicate parameters which may be repeated. Command names are shown in *bold*
and _underscored_ text is to be replaced with a value of the user's choosing.
Text with no styling is to be used literally.
The command may accept optional (or mandatory) options, which are preceeded
with a dash ("-") and are one character in length. If an option accepts a
value, the value may be specified immediately following it (e.g. -ovalue) or as
the next parameter (e.g. -o value). Options which do not accept a value may be
specified together (e.g. -abc). An option which accepts a value may also be
specified as the last of several options (e.g. -abcovalue, specifying -abc and
The first non-option parameter indicates the start of the arguments, and each
following parameters is considered such as well. A "--" parameter may also be
used to signal the end of options, allowing the following parameter to begin
with "-" and be interpreted an argument.
## EXIT STATUS
Unless otherwise specified, all commands will exit with status code *0* on
success or a value *>0* on error.
Unless otherwise specified, all programs use _stdin_ for input, _stdout_ for
output, and _stderr_ to communicate diagnostic messages.
*ctools* provides POSIX-1.2017-compatible "base utilities" with optional
support for the XSI option. This man page is not intended to be a complete
reference, and where it disagrees with the specification, the specification
takes precedence. The *at*(1), *batch*(1), and *crontab*(1) commands are also
optional, and may not be present on your system.
A shell (*sh*(1)) is not provided by *ctools*.