C Programming Code Examples
C > Strings Code Examples
Add spaces to the end of a string
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/* Add spaces to the end of a string */
#include <stdio.h>
#include <string.h>
void pad(char *s, int length);
int main(void)
{
char str[200];
strcpy(str, "c.happycodings.com - C Programming Language Code Examples");
pad(str, 40);
printf("%d", strlen(str));
return 0;
}
void pad(char *s, int length)
{
int l;
l = strlen(s); /* its length */
while(l<length) {
s[l] = ' '; /* insert a space */
l++;
}
s[l]= '\0'; /* strings need to be terminated in a null */
}
printf() Function in C
Writes the C string pointed by format to the standard output (stdout). If format includes format specifiers (subsequences beginning with %), the additional arguments following format are formatted and inserted in the resulting string replacing their respective specifiers.
printf format string refers to a control parameter used by a class of functions in the input/output libraries of C programming language. The string is written in a simple template language: characters are usually copied literally into the function's output, but format specifiers, which start with a % character, indicate the location and method to translate a piece of data (such as a number) to characters. "printf" is the name of one of the main C output functions, and stands for "print formatted". printf format strings are complementary to scanf format strings, which provide formatted input (parsing). In both cases these provide simple functionality and fixed format compared to more sophisticated and flexible template engines or parsers, but are sufficient for many purposes.
Syntax for printf() function in C
#include <stdio.h>
int printf ( const char * format, ... );
format
C string that contains the text to be written to stdout.
It can optionally contain embedded format specifiers that are replaced by the values specified in subsequent additional arguments and formatted as requested.
A format specifier follows this prototype: [see compatibility note below]
%[flags][width][.precision][length]specifier
Where the specifier character at the end is the most significant component, since it defines the type and the interpretation of its corresponding argument:
specifier
a conversion format specifier.
d or i
Signed decimal integer
u
Unsigned decimal integer
o
Unsigned octal
x
Unsigned hexadecimal integer
X
Unsigned hexadecimal integer (uppercase)
f
Decimal floating point, lowercase
F
Decimal floating point, uppercase
e
Scientific notation (mantissa/exponent), lowercase
E
Scientific notation (mantissa/exponent), uppercase
g
Use the shortest representation: %e or %f
G
Use the shortest representation: %E or %F
a
Hexadecimal floating point, lowercase
A
Hexadecimal floating point, uppercase
c
Character
s
String of characters
p
Pointer address
n
Nothing printed. The corresponding argument must be a pointer to a signed int. The number of characters written so far is stored in the pointed location.
%
A % followed by another % character will write a single % to the stream.
The format specifier can also contain sub-specifiers: flags, width, .precision and modifiers (in that order), which are optional and follow these specifications:
flags
one or more flags that modifies the conversion behavior (optional)
-
Left-justify within the given field width; Right justification is the default (see width sub-specifier).
+
Forces to preceed the result with a plus or minus sign (+ or -) even for positive numbers. By default, only negative numbers are preceded with a - sign.
(space)
If no sign is going to be written, a blank space is inserted before the value.
#
Used with o, x or X specifiers the value is preceeded with 0, 0x or 0X respectively for values different than zero. Used with a, A, e, E, f, F, g or G it forces the written output to contain a decimal point even if no more digits follow. By default, if no digits follow, no decimal point is written.
0
Left-pads the number with zeroes (0) instead of spaces when padding is specified (see width sub-specifier).
width
an optional * or integer value used to specify minimum width field.
(number)
Minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger.
*
The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.
.precision
an optional field consisting of a . followed by * or integer or nothing to specify the precision.
.number
For integer specifiers (d, i, o, u, x, X): precision specifies the minimum number of digits to be written. If the value to be written is shorter than this number, the result is padded with leading zeros. The value is not truncated even if the result is longer. A precision of 0 means that no character is written for the value 0.
For a, A, e, E, f and F specifiers: this is the number of digits to be printed after the decimal point (by default, this is 6).
For g and G specifiers: This is the maximum number of significant digits to be printed.
For s: this is the maximum number of characters to be printed. By default all characters are printed until the ending null character is encountered.
If the period is specified without an explicit value for precision, 0 is assumed.
.*
The precision is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.
length
an optional length modifier that specifies the size of the argument.
... (additional arguments)
Depending on the format string, the function may expect a sequence of additional arguments, each containing a value to be used to replace a format specifier in the format string (or a pointer to a storage location, for n).
There should be at least as many of these arguments as the number of values specified in the format specifiers. Additional arguments are ignored by the function.
If a writing error occurs, the error indicator (ferror) is set and a negative number is returned.
If a multibyte character encoding error occurs while writing wide characters, errno is set to EILSEQ and a negative number is returned.
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/* print formatted data to stdout by printf() function example */
#include <stdio.h>
int main()
{
char ch;
char str[100];
int a;
float b;
printf("Enter any character \n");
scanf("%c", &ch);
printf("Entered character is %c \n", ch);
printf("Enter any string ( upto 100 character ) \n");
scanf("%s", &str);
printf("Entered string is %s \n", str);
printf("Enter integer and then a float: ");
// Taking multiple inputs
scanf("%d%f", &a, &b);
printf("You entered %d and %f", a, b);
return 0;
}
strlen() Function in C
Get string length. Returns the length of the C string str. The length of a C string is determined by the terminating null-character: A C string is as long as the number of characters between the beginning of the string and the terminating null character (without including the terminating null character itself).
Syntax for strlen() Function in C
#include <string.h>
size_t strlen ( const char * str );
str
C string
Function returns the length of string.
This should not be confused with the size of the array that holds the string.
strlen() function is defined in string.h header file. It doesn't count null character '\0'.
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/* get the length of the C string str by strlen() function example */
/* Program to find the total length of a String using strlen() */
#include<stdio.h>
#include<string.h>
int main()
{
char str1[10]= "01234567"; /* First string */
printf("First String is %s",str1);
printf("\n");
int length = strlen(str1);
printf("Length of first String is %d", length);
printf("\n");
char str2[20]= "String Chapter"; /* Second string */
printf("Second String is %s",str2);
printf("\n");
length = strlen(str2);
printf("Length of second String is %d", length);
return 0;
}
#include Directive in C
#include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C/C++ program. This directive is read by the preprocessor and orders it to insert the content of a user-defined or system header file into the following program. These files are mainly imported from an outside source into the current program. The process of importing such files that might be system-defined or user-defined is known as File Inclusion. This type of preprocessor directive tells the compiler to include a file in the source code program. Here are the two types of file that can be included using #include:
• Header File or Standard files: This is a file which contains C/C++ function declarations and macro definitions to be shared between several source files. Functions like the printf(), scanf(), cout, cin and various other input-output or other standard functions are contained within different header files. So to utilise those functions, the users need to import a few header files which define the required functions.
• User-defined files: These files resembles the header files, except for the fact that they are written and defined by the user itself. This saves the user from writing a particular function multiple times. Once a user-defined file is written, it can be imported anywhere in the program using the #include preprocessor.
Syntax for #include Directive in C
#include "user-defined_file"
#include <header_file>
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/* #include directive tells the preprocessor to insert the contents of another file into the source code at the point where the #include directive is found. */
// C program to illustrate file inclusion
// <> used to import system header file
#include <stdio.h>
// " " used to import user-defined file
#include "process.h"
// main function
int main()
{
// add function defined in process.h
add(10, 20);
// mult function defined in process.h
multiply(10, 20);
// printf defined in stdio.h
printf("Process completed");
return 0;
}
main() Function in C
In C, the "main" function is treated the same as every function, it has a return type (and in some cases accepts inputs via parameters). The only difference is that the main function is "called" by the operating system when the user runs the program. Thus the main function is always the first code executed when a program starts.
main() function is a user defined, body of the function is defined by the programmer or we can say main() is programmer/user implemented function, whose prototype is predefined in the compiler. Hence we can say that main() in c programming is user defined as well as predefined because it's prototype is predefined.
main() is a system (compiler) declared function whose defined by the user, which is invoked automatically by the operating system when program is being executed.
Its first function or entry point of the program from where program start executed, program's execution starts from the main. So main is an important function in c , c++ programming language.
Syntax for main() Function in C
void main()
{
.........
// codes start from here
.........
}
void
is a keyword in C language, void means nothing, whenever we use void as a function return type then that function nothing return. here main() function no return any value.
In place of void we can also use int return type of main() function, at that time main() return integer type value.
main
is a name of function which is predefined function in C library.
• An operating system always calls the main() function when a programmers or users execute their programming code.
• It is responsible for starting and ends of the program.
• It is a universally accepted keyword in programming language and cannot change its meaning and name.
• A main() function is a user-defined function in C that means we can pass parameters to the main() function according to the requirement of a program.
• A main() function is used to invoke the programming code at the run time, not at the compile time of a program.
• A main() function is followed by opening and closing parenthesis brackets.
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/* basic c program by main() function example */
#include <stdio.h>
#include <conio.h>
main()
{
printf (" It is a main() function ");
int fun2(); // jump to void fun1() function
printf ("\n Finally exit from the main() function. ");
}
void fun1()
{
printf (" It is a second function. ");
printf (" Exit from the void fun1() function. ");
}
int fun2()
{
void fun1(); // jump to the int fun1() function
printf (" It is a third function. ");
printf (" Exit from the int fun2() function. ");
return 0;
}
While Loop Statement in C
While loop is also known as a pre-tested loop. In general, a while loop allows a part of the code to be executed multiple times depending upon a given boolean condition. It can be viewed as a repeating if statement. The while loop is mostly used in the case where the number of iterations is not known in advance.
The while loop evaluates the test expression inside the parentheses (). If test expression is true, statements inside the body of while loop are executed. Then, test expression is evaluated again. The process goes on until test expression is evaluated to false. If test expression is false, the loop terminates.
Syntax of While Loop Statement in C
while (testExpression) {
// the body of the loop
}
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/* while loop statement in C language */
#include<stdio.h>
int main()
{
int n, num, sum = 0, remainder;
printf("Enter a number: ");
scanf("%d", &n);
num = n;
// keep looping while n > 0
while( n > 0 )
{
remainder = n % 10; // get the last digit of n
sum += remainder; // add the remainder to the sum
n /= 10; // remove the last digit from n
}
printf("Sum of digits of %d is %d", num, sum);
// signal to operating system everything works fine
return 0;
}
strcpy() Function in C
Copy string. Copies the C string pointed by source into the array pointed by destination, including the terminating null character (and stopping at that point).
To avoid overflows, the size of the array pointed by destination shall be long enough to contain the same C string as source (including the terminating null character), and should not overlap in memory with source.
Syntax for strcpy() Function in C
#include <string.h>
char * strcpy ( char * destination, const char * source );
destination
Pointer to the destination array where the content is to be copied.
source
C string to be copied.
Destination is returned.
strcpy() is a standard library function in C/C++ and is used to copy one string to another. In C it is present in string.h header file. Function copies the string pointed by source (including the null character) to the destination.
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/* copy one string to another by strcpy() function example */
#include<stdio.h>
#include<string.h>
int main()
{
char ch_arr1[20];
char ch_arr2[20];
printf("Enter first string (ch_arr_1): ");
gets(ch_arr1);
printf("Enter second string(ch_arr_1): ");
gets(ch_arr2);
printf("\nCopying first string into second... \n\n");
strcpy(ch_arr2, ch_arr1); // copy the contents of ch_arr1 to ch_arr2
printf("First string (ch_arr_1) = %s\n", ch_arr1);
printf("Second string (ch_arr_2) = %s\n", ch_arr2);
printf("\nCopying \"Greece\" string into ch_arr1 ... \n\n");
strcpy(ch_arr1, "Greece"); // copy Greece to ch_arr1
printf("\nCopying \"Slovenia\" string into ch_arr2 ... \n\n");
strcpy(ch_arr2, "Slovenia"); // copy Slovenia to ch_arr2
printf("First string (ch_arr_1) = %s\n", ch_arr1);
printf("Second string (ch_arr_2) = %s\n", ch_arr2);
// signal to operating system program ran fine
return 0;
}
Program code display 'Fibonacci series' using recursion. Using "fibonacci_series()" that calls itself recursively, in order to display series for the entered number of terms. Program enter
First give a meaningful name to our recursive function say pow(). The function must accept 2 numbers i.e. base. exponent and calculate its power. Hence, take 2 parameters for base
Program take two numbers and a operator as input and store it in the variables a, b and ch respectively. Using switch statement, test the operator stored in the variable ch. Print the
Function expression, array expression, unary minus, structure operators, increment and decrement, one's compliment, left and right shift, size of operator, pointer operators, type
Instead of using Nested If Else. Lets combine 2 or more conditions together using Logical Operators. A number j1 among 3 numbers j1, j2 and j3 is said maximum if j1 > j2 and j1 > j3.
