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String Function in C with Examples

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4th Dec, 2022
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String Function in C with Examples

String Functions in C can be referred to as an array of characters that tend to discontinue a null and void symbol, for instance, “/0”. Firstly, it is crucial to understand the difference between a string and an array of characters. The former receives a null character in the end, unlike the latter, which necessarily does not have to end with so. 

Strings are often modified and used in various operations that fit the requirements. A loop is used to calculate the length of the string, although it is not the best option for other complex purposes. This is why String Functions in C are essential to code directly and efficiently. 

What are the most common examples of String Functions?

Several String Functions in C are used on a large basis. The following are:

  • Strcat: The purpose of this function() is to attach the source string’s copy to the concluding portion of the string. The Strcat() functions lead toward certain arguments:
    1) dest
    2) src

You will find a copy attached to the concluding part of the string. The first character of SRC works as a replacement for the last character present in the whole string.

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For example:

#include <cstring>
#include <iostream>
Using namespace std; int main ()

Char dest [50] = “This is an”
Char src [50] = “example”
STRCAT (dest,src)

  • Strrchr: When it comes to C++, Strrchr performs majorly on string handling. The CString is primarily used in the header files. A pointer is mainly returned to the concluding portion of a string. 

Examples of such syntax include:
Strrchr (const char*str, int c)
Here, STR is the string, and C is the character that should be put in.
Output: String after the last e is: eks
String after the last m is: null

  • Strcmp: Strcmp function in C () can be understood as an in-built library function, commonly viewed in the <string.h> header file. Two strings are taken as arguments and are compared in a lexicographical manner.
    Syntax: int strcmp (const char *leftStr, const char *rightStr)

The given prototype mentions two strings for parameters, ending it with an integer value in terms of the comparison within both the strings.

  • If both the strings are equal, the second character is used to check, and if it is found to be the same, a third character is checked.
  • This process is continued until one of the characters in the string returns null, or both the characters are found to be unequal.
  • Strcpy: One of the most used functions in C++, Strcpy is a library function required to copy one string from another string. It is also used in C at times present, especially in string.h header file.
    Syntax: char* strcpy (char*dest, const char*src)
    Parameters: str: It is required to measure the string variable in order to find the string’s length.
  • Strncat: Considered to be a predefined function in terms of string handling, strncat is used both in C as well as C++.  In this case, string.h is the header file highly required for string functions. This function attaches not more than n characters from the string, which is directed by a null character. The starting character tends to overwrite the null character, which can be found at the end of every string. This is why string dest becomes strlen dest (n+). 

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However, all of this may go wrong once:

  • The strings are overlapping
  • The dest array is not large enough to attach src contents
  • Dest: The string which is required to be attached
  • Src: The string from which “n characters” are not going to be attached
  • N: refers to the maximum characters
  • Strlen: This particular function tends to calculate the length of the provided string. [/0] is not referred to as the null character in this scenario.
    Syntax: int strlen (const char*str)
    Parameter: The length is considered the main objective in the string length.
  • Strncmp: This function focuses mainly on the count characters on the string and returns an integer specified as per the outcome.
  • Two strings are taken, and a number num is considered as an argument so that both can be compared. 
  • It is compulsory for num to be equal to the longest string’s length. 
  • A comparison between the two strings takes place in a lexicographical manner. 
  • This process leads to a conclusion once a null character is reached or the num characters of both strings become identical.
  • Strncpy: Similar to strcpy() function,  the Strncpy function has most n bytes of src as copied. If there is a lack of null characters in the string, it is not null-terminated. If the length is less than n, total n characters are mentioned along with an additional null character.
    Syntax: char *strncpy (char*dest, const char* src, size t_n)
    Src: String is to be copied
    Dest: Pointer where the content is copied

N: This is the first n character

  • Strrchr: This function () is applicable in all C/C++ programming languages. It is used to pinpoint the last portion present in a string. Considered as a part of the C String, it is necessary to reclaim a pointer towards the string’s end. The last null character is understood as the terminating portion of the C string. This is why it is referred to as the CString header file.
    Syntax: char* strrchr ( char*str, int ch)
    Parameter: str: focuses mainly on the pointer to the null-terminated string.

Ch: This refers to the character which is required to be searched.

Hence, String Functions in C have a number of examples that could be used, especially in C/C++ programming languages. 

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Which is the most commonly used String Function? 

Strstr in C can be referred to as the predefined function required in string handling at a massive level. String h is the noted header line for string functions.
This function requires two strings, S1 and S2, to find the occurrence of both these strings. The terminating null characters are not included in the string, which is why the occurrence can be understood as the main function.
char * strstr (const char * S1, const char *S2)
Parameters: S1- Main string to be examined
S2- Sub-string, which is also present in the S1 string
Return value: The pointer is returned once the first character is already located in S2 of S1. If S2 suggests that it’s an empty string, S1 is brought back again. 

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Summing Up: 

As we saw, string functions focus on making codes efficient and straightforward. The best perk of String Functions in C is that they are already pre-written, leading to direct usage. As it is one of the most important software developments, you must learn the basics of this language. With a beginner level of difficulty, it is the ideal programming language you can start with. Upgrad’s Executive PG Program in Software Development-Full Stack Development can be regarded as the ideal fit if you are trying your hands at String Functions. 

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Pavan Vadapalli

Blog Author
Director of Engineering @ upGrad. Motivated to leverage technology to solve problems. Seasoned leader for startups and fast moving orgs. Working on solving problems of scale and long term technology strategy.
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