From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Sun, 27 Jan 2008 11:37:44 +0100 Subject: Initial import (2.0.2-6) --- reference/C/FUNCTIONS/format.html | 315 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 315 insertions(+) create mode 100644 reference/C/FUNCTIONS/format.html (limited to 'reference/C/FUNCTIONS/format.html') diff --git a/reference/C/FUNCTIONS/format.html b/reference/C/FUNCTIONS/format.html new file mode 100644 index 0000000..0d18e69 --- /dev/null +++ b/reference/C/FUNCTIONS/format.html @@ -0,0 +1,315 @@ +printf format identifiers. + + + + +
+
+

printf format identifiers.

+
+
+

+printf formatting is controlled by 'format identifiers' which, are shown +below in their simplest form. +

+

+ + + + +
+
+
+    %d %i     Decimal signed integer.
+    %o	      Octal integer.
+    %x %X     Hex integer.
+    %u	      Unsigned integer.
+    %c	      Character.
+    %s	      String. See below.
+    %f	      double
+    %e %E     double.
+    %g %G     double.
+    %p        pointer.
+    %n	      Number of characters written by this printf.
+              No argument expected.
+    %%	      %. No argument expected.
+
+
+
+
+

+ +These identifiers actually have upto 6 parts as shown in the table below. +They MUST be used in the order shown. +

+ +

+ + + + + + + + + + + + + + + + +
%FlagsMinimum field widthPeriodPrecision. Maximum field widthArgument type
RequiredOptionalOptionalOptionalOptionalRequired
+
+

+ + +

+

%

+The % marks the start and therfore is manatory. +

+ + +

+

Flags

+The format identifers can be altered from their default function by +applying the following flags: +

+ +

+ + + + +
+
+
+   -      Left justify.
+   0  	  Field is padded with 0's instead of blanks.
+   +	  Sign of number always O/P.
+   blank  Positive values begin with a blank.
+   # 	  Various uses:
+	  %#o (Octal) 0 prefix inserted.
+	  %#x (Hex)   0x prefix added to non-zero values.
+	  %#X (Hex)   0X prefix added to non-zero values.
+	  %#e         Always show the decimal point.
+	  %#E         Always show the decimal point.
+	  %#f         Always show the decimal point.
+	  %#g         Always show the decimal point trailing 
+	  	      zeros not removed.
+	  %#G         Always show the decimal point trailing
+		      zeros not removed.
+          
+
+
+
+ + +Here are a few more examples. +

+ +

+ + + + +
+
+
+    printf(" %-10d \n", number);
+    printf(" %010d \n", number);
+    printf(" %-#10x \n", number);  
+    printf(" %#x \n", number);
+
+
+
+ +

+ +

+

Minimum field width.

+By default the width of a field will be the minimum required to hold +the data. If you want to increase the field width you can use the +following syntax. +

+

+ + + + +
+
+
+  main()
+  {
+      int number    =  5;
+      char *pointer = "little";
+
+      printf("Here is a number-%4d-and a-%10s-word.\n", number, pointer);
+  }
+  
+  /*********************************
+   *
+   *	Program result is:
+   *
+   * 	Here is a number-   5-and a-    little-word.
+   *
+   *********************************/
+
+
+
+

+As you can see, the data is right justified within the field. It can +be left justified by using the - flag. +A maximum string width can also be specified. +

+The width can also be given as a variable as shown below. +

+

+ + + + +
+
+
+    main()
+    {
+        int number=5;
+
+        printf("---%*d----\n", 6, number);
+    }
+  
+    /*********************************
+     *
+     *    Program result is:
+     *
+     *    ----     5---
+     *
+     *********************************/
+
+
+
+

+The * is replaced with the supplied int to provide the ability to +dynamically specify the field width. +

+

+ +

Period

+If you wish to specify the precision of an argument, +it MUST be prefixed with the period. +

+ +

+

Precision

+ +The Precision takes different meanings for the different format types. + +

Float Precision

+
+	%8.2f
+
+This says you require a total field of 8 characters, within the 8 +characters the last 2 will hold the decimal part. + +
+	%.2f
+
+ +The example above requests the minimum field width and the last two +characters are to hold the decimal part. + +

Character String Maximum field width

+ +The precision within a string format specifies the maximum +field width. +
+	%4.8s
+
+Specifies a minimum width of 4 and a maximum width +of 8 characters. If the string is greater than 8 characters, +it will be cropped down to size. +

+ +Here is a little program +that shows an alternative to strncpy. + +

* Precision

+ +As with the 'width' above, the precision does not have to be hard +coded, the * symbol can be used and an integer supplied to give its +value. +

+

+ +

Format Identifiers

+The format identifier describes the expected data. The identifier is the +character that ends +Here is a list of the format identifers as used in 'printf' ,'sprintf' +,'fprintf' and 'scanf'. + +
    +
  1. Except for '%' and 'n', all the identifiers expect to extract an argument +from the printf parameter list. +
  2. All of the parmameters should be the value +to be inserted. EXCEPT %s, this expects a +pointer to be passed. +
+

An example.

+

+

+ + + + +
+
+
+	main()
+        {
+            int number=5;
+	    char *pointer="little";
+
+	    printf("Here is a number %d and a %s word.\n", number, pointer);
+	}
+	/*********************************
+	 *
+	 *	Program result is:
+	 *
+	 * 	Here is a number 5 and a little word.
+	 *
+	 *********************************/
+
+
+
+

+ +

+

+

+ + + + +
+ Top + + Master Index + + Keywords + + Functions +
+
+

+

+
Martin Leslie +

+ + -- cgit v1.2.3-54-g00ecf