Difference between revisions of "sysutils"

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(Caveats: give program code better title, allegedly insert new external links [spam detection false positive])
 
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'''SysUtils''' is a basic library containing various system utilities
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{{sysutils}}
  
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The [[Unit|unit]] '''<syntaxhighlight lang="pascal" inline>sysUtils</syntaxhighlight>''' shipped with the [[FPC|FPC’s]] default [[RTL|run-time library]] provides many system utilities.
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It attempts to be as compatible to [[Delphi|Delphi’s]] <syntaxhighlight lang="pascal" inline>sysUtils</syntaxhighlight> unit as possible.
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However, the FPC version is available on [[Platform list|all platforms that the FPC supports]].
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It does not contain any Windows-related routines or other highly platform-specific functionality.
  
For details see: [http://www.freepascal.org/docs-html/rtl/sysutils/index.html freepascal.org sysutils]
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== Notable functionality ==
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* [[Format function|<syntaxhighlight lang="pascal" inline>format</syntaxhighlight>]]
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* [[Executing External Programs#SysUtils.ExecuteProcess|<syntaxhighlight lang="pascal" inline>executeProcess</syntaxhighlight> for executing external programs]]
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* several routines ensuring productive use of [[TDateTime|<syntaxhighlight lang="pascal" inline>tDateTime</syntaxhighlight>]]
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* {{Doc|package=RTL|unit=sysutils|identifier=typehelpers|text=type helpers for all basic data types}}
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* [[FreeAndNil|<syntaxhighlight lang="pascal" inline>freeAndNil</syntaxhighlight>]]
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* routines to access [[Command line parameters and environment variables#Environment variables|environment variables]]
  
[[Category:Units]]
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== Caveats ==
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{{Doc|package=RTL|unit=system|identifier=runtimeerrors|text=If the <syntaxhighlight lang="pascal" inline>sysUtils</syntaxhighlight> unit is included}}, all [[runtime error|run-time errors]] become [[Exceptions|exceptions]], which virtually forces you to use a [[Compiler Mode|compiler mode]] (or [[modeswitch|mode switch]]) that allows exception treatment.
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To catch an exception by its name you will need to include <syntaxhighlight lang="pascal" inline>sysUtils</syntaxhighlight>, even though the module itself does not use any of the included system utilities.
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Changing run-time errors to exceptions has a ''global'' effect.
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The following program will terminate with an uncaught ''exception'', even though it does not list <syntaxhighlight lang="pascal" inline>sysUtils</syntaxhighlight> in its <syntaxhighlight lang="delphi" inline>uses</syntaxhighlight>-clause:
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The <syntaxhighlight lang="pascal" inline>sysUtils</syntaxhighlight> unit is ''implicitly'' included via the {{Doc|package=RTL|unit=strutils|text=<syntaxhighlight lang="pascal" inline>strUtils</syntaxhighlight> unit}}:
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<syntaxhighlight lang="pascal">
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program implicitSysUtilsCaveat(input, output, stdErr);
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uses
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strUtils;
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var
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x: file of char;
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c: char;
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begin
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// deliberately cause an error for demonstration purposes
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read(x, c);
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end.
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</syntaxhighlight>
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Also, if [[Size Matters|size matters]], using <syntaxhighlight lang="pascal" inline>sysUtils</syntaxhighlight> is by design not the smartest choice.
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== See also ==
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* {{Doc|package=RTL|unit=sysutils|text=<syntaxhighlight lang="pascal" inline>sysUtils</syntaxhighlight> reference}}
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* [http://docwiki.embarcadero.com/Libraries/Sydney/en/System.SysUtils Delphi’s <syntaxhighlight lang="pascal" inline>sysUtils</syntaxhighlight> unit]
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* [[libc library|<syntaxhighlight lang="c" inline>libc</syntaxhighlight> library]] <!-- similar in design -->
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* [[System unit|<syntaxhighlight lang="pascal" inline>system</syntaxhighlight> unit]]

Latest revision as of 18:48, 6 February 2021

English (en) français (fr)

The unit sysUtils shipped with the FPC’s default run-time library provides many system utilities. It attempts to be as compatible to Delphi’s sysUtils unit as possible. However, the FPC version is available on all platforms that the FPC supports. It does not contain any Windows-related routines or other highly platform-specific functionality.

Notable functionality

Caveats

If the sysUtils unit is included, all run-time errors become exceptions, which virtually forces you to use a compiler mode (or mode switch) that allows exception treatment. To catch an exception by its name you will need to include sysUtils, even though the module itself does not use any of the included system utilities.

Changing run-time errors to exceptions has a global effect. The following program will terminate with an uncaught exception, even though it does not list sysUtils in its uses-clause: The sysUtils unit is implicitly included via the strUtils unit:

program implicitSysUtilsCaveat(input, output, stdErr);
uses
	strUtils;
var
	x: file of char;
	c: char;
begin
	// deliberately cause an error for demonstration purposes
	read(x, c); 
end.

Also, if size matters, using sysUtils is by design not the smartest choice.

See also