Skip to main content

String handling functions in C

Like numbered arrays, C handles character arrays (strings).

  1. Each string is identified as a character array and ends with a ‘\0’(null) character (the compiler automatically adds the null character). So the end of string is identified as a null character.
  2. Being an array, all the elements of the string array stored in continuous memory locations

following is the declaration of character array

char name[50];

or

char name[]=”Pradeep Kumar”;

or

char name[20]=”Hello Pradeep”;

Strings can be handled or manipulated through loops or library functions. There are some library functions to handle strings are available at string.h

Some of them are

strlen(string) 

  • This is to find the length of the string and returns an integer
  • For example, if “Hello” is the string, the length will be 5 and “Hello “, the length is 6 (there is a blank space after o in hello)

strcat(String1, string2)

  • to concatenate two strings
  • One string will be appended to another string (the concatenation happens by inserting the new string at the null character ‘\0’ of the first string)
  • Example, if String1 is “Hello” and String2 is “Pradeep”, then strcat(string1, string2) will be “HelloPradeep”
  • Similarly,  if String1 is “Hello ” and String2 is “Pradeep”, then strcat(string1, string2) will be “Hello Pradeep”

strcpy(Destination, source)

  • This function is to copy one string to other
  • usually the copying string will be the 2nd parameter and copied string will be the first parameter
  • Example, if string1 is “Bad” and string2 is “Good” the strcpy(string1,string2) will give Good for string1

strcmp(Destination, source)

  • This function is to compare two strings whether they are equal or not
  • like numbers, two strings should not be compared directly like if(a==b)
  • If both the strings are equal, the function returns 0, else it will return the difference of ASCII value of the first non matching characters
  • Example, strcmp(“Their”, “There”) will return ASCII(i) – ASCII(r) (an integer will be returned)

Example Program

//program to demonstrate string handling functions
#include <stdio.h>
#include <conio.h>
int main()
{
    char a[50];
    char b[50];
    printf("Please the two strings one by one\n");
    gets(a);
    gets(b);
    printf("Length of String a is %d \n",strlen(a));
    printf("Length of String b is %d \n",strlen(b));
    if(!strcmp(a,b))  //Comparing two string will return 0, ! before strcmp() is needed
    printf("Both the strings are Equal");
    else
    printf("Both the strings are not equal");
    strcat(a,b);  //Concatenation function
    printf("the concatenated String is:");
    puts(a);
    strrev(a);
    printf("The reverse string is\n");
    puts(a);
    getch();
    return 0;
}
   
   

In the above program , instead of gets() function, scanf() can be used, but the disadvantage of scanf() being it truncates the blank space, new line, form feed, tab.

So for example, if the input give is “Hello pradeep”, then Hello only will be accepted, the string after the blank space will be omitted by the compiler, so gets() can be used.

Similarly, puts() or printf() can be used to display strings.

Comments

Popular posts from this blog

Installation of NS2 (ns-2.35) in Ubuntu 20.04

Installation of NS2 (ns-2.35) in Ubuntu 20.04 LTS Step 1: Install the basic libraries like      $] sudo apt install build-essential autoconf automake libxmu-dev Step 2: install gcc-4.8 and g++-4.8 open the file using sudo mode $] sudo nano /etc/apt/sources.list Include the following line deb http://in.archive.ubuntu.com/ubuntu bionic main universe $] sudo apt update $] sudo apt install gcc-4.8 g++-4.8 Step 3:  Unzip the ns2 packages to home folder $] tar zxvf ns-allinone-2.35.tar.gz $] cd ns-allinone-2.35/ns-2.35 Modify the following make files. ~ns-2.35/Makefile.in Change @CC@ to gcc-4.8 change @CXX@ to g++-4.8 ~nam-1.15/Makefile.in ~xgraph-12.2/Makefile.in ~otcl-1.14/Makefile.in Change in all places  @CC@ to gcc-4.8 @CPP@ or @CXX@ to g++-4.8 open the file: ~ns-2.35/linkstate/ls.h Change at the Line no 137  void eraseAll() { erase(baseMap::begin(), baseMap::end()); } to This void eraseAll() { this->erase(baseMap::begin(), baseMap::end()); } All changes made Step 4: Open a new termi

Installing ns-3.34 in Ubuntu 20.04

This post shows how to install ns 3.34 in Ubuntu 20.04 LTS Prerequisites: Fresh installation of Ubuntu Version 20.04 LTS  ns3.34 can be downloaded from here Follow the video link for complete step by step instructions on the installation.  This version fixes the compilation issues of vanet-routing-compare.cc (bug in ns3.33)  Issue the following commands after opening a terminal  $ sudo apt update $ sudo apt install g++ python3 python3-dev python-dev pkg-config sqlite3 python3-setuptools git qt5-default gir1.2-goocanvas-2.0 python3-gi python3-gi-cairo python3-pygraphviz gir1.2-gtk-3.0 ipython3 openmpi-bin openmpi-common openmpi-doc libopenmpi-dev autoconf cvs bzr unrar openmpi-bin openmpi-common openmpi-doc libopenmpi-dev tcpdump wireshark libxml2 libxml2-dev Unzip or untar the ns-allinone-3.34.tar.bz2 in the home folder (in my case its /home/pradeepkumar) $ cd ns-allinone-3.34/ $ ./build.py --enable-examples --enable-tests  Once the installation is completed, you may get an output show

Installation of ns3 in Windows 10 and Windows 11 OS using WSL (Windows Subsystem for Linux)

This post shows how to install ns-3.33 in Windows 10 through WSL (Windows Subsystem for Linux) This posts works for Windows 11 also (I have tested it on a Windows 11 ISO and it works the Same way as mentioned in the following post.) This post will work for ns-3.3x version. Prerequisites : Install Windows Subsystem for Linux with GUI: Please refer the following video  System Information: OS used: Windows 10 and WSL (Ubuntu 20.04) GUI: XServer for Windows NS3 Version: ns-3.33 See the following complete video on how to install ns3 in Windows 10 Step 0 : Open XLaunch Step 1 :  Open WSL using PowerShell and open it as Administrator Command:/  wsl $ xfce4-session The GUI of Ubuntu Opens within Windows 10 OS. Step 2 : Download ns3 from nsnam.org website through Mozilla Firefox browser Step 3: Open a Terminal  $ sudo apt update $ sudo apt install build-essential autoconf automake libxmu-dev python3-pygraphviz cvs mercurial bzr git cmake p7zip-full python3-matplotlib python-tk python3-dev qt5-q