C Method Signature Examples

This repository contains simple C programs demonstrating different forms of the main function signature in C, and how command-line arguments and environment variables are handled.

Files

• noparameterlist.c

  • Demonstrates int main(void)
  • No external input is taken, only prints internal messages.
  • Run example:

    gcc noparameterlist.c -o noparameter
    ./noparameter > outputNoParameterList.txt
    ./noparameter hi hope > outputNoParameterList.txt

• parameterlist2.c

  • Demonstrates int main(int argc, char *argv[])
  • Accepts command-line arguments and prints them.
  • Run example:

    gcc parameterlist2.c -o param2
    ./param2 hi this is a ball 73 62 > outputParameterList2.txt
    ./param2 > outputParameterList1.txt

• parameterlistwithenv.c

  • Demonstrates int main(int argc, char *argv[], char *envp[])
  • Prints command-line arguments and environment variables.
  • Run example:

    gcc parameterlistwithenv.c -o paramenv
    MYVAR=Hello ./paramenv hi this is a ball 73 62 > outputParameterListwithEnv2.txt
    ./paramenv hi this is a ball 73 62 > outputParameterListwithEnv1.txt

Outputs

• outputNoParameterList.txt → Output of noparameterlist.c
• outputParameterList1.txt → Output of parameterlist2.c with no arguments
• outputParameterList2.txt → Output of parameterlist2.c with arguments
• outputParameterListwithEnv1.txt → Output of parameterlistwithenv.c with arguments
• outputParameterListwithEnv2.txt → Output of parameterlistwithenv.c with arguments + custom environment variable

Notes

• argc is the count of arguments.
• argv is the list of command-line arguments (argv[0] = program name).
• envp is the list of environment variables in the form NAME=VALUE.
• Always loop using i < argc to avoid undefined behavior.

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✅ This repository is useful for understanding different signatures of main in C and how to work with external and internal inputs.