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#define BUFFER$\_$SIZE $1024//$ Define a constant for the buffer size

$/**$

$*$ Function: copy$\_$file

$*-------------------$

$*$ Copies the content from the source file to the destination file using system calls.

$*$

$*$ Parameters:

$*-$ source: The path of the source file $($file to copy from$).$

$*-$ destination: The path of the destination file $($file to copy to$).$

$*$

$*$ Write File Permissions: $($Must use these file permissions$)$

$*$ S$\_$IRUSR: Owner has read permission.

$*$ S$\_$IWUSR: Owner has write permission.

$*$ S$\_$IRGRP: Group has read permission.

$*$ S$\_$IROTH: Others have read permission.

$*$

$*$ Returns:

$*0$ on success

$*-1$ on failure $($if an error occurs while opening, reading, or writing the files$).$

$*$

$*$ System calls that MUST be used:

$*-$ open$()$: Opens the source and destination files.

$*-$ read$()$: Reads the content from the source file.

$*-$ write$()$: Writes the content to the destination file.

$*-$ close$()$: Closes the files after the operation.

$*/$

int copy$\_$file$($const char $*$source$,$ const char $*$destination$)$

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$/**$

$*$ Function: get$\_$env$\_$var

$*---------------------$

$*$ Retrieves the value of an environment variable.

$*$

$*$ Parameters:

$*-$ var$\_$name: The name of the environment variable to retrieve.

$*$

$*$ Returns:

$*-$ The value of the environment variable if it exists.

$*-$ A message "Environment variable not found" if the variable is not found.

$*$

$*$ This function uses the standard library function getenv$()$ to get the value.

$*/$

const char $*$get$\_$env$\_$var$($const char $*$var$\_$name$)$

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$/**$

$*$ Function: set$\_$env$\_$var

$*---------------------$

$*$ Sets or updates the value of an environment variable.

$*$

$*$ Parameters:

$*-$ var$\_$name: The name of the environment variable to set.

$*-$ value: The value to assign to the environment variable.

$*-$ overwrite: Determines whether to overwrite the variable if it already exists.

$*-1$ to overwrite, $0$ to prevent overwriting.

$*$

$*$ Returns:

$*0$ on success.

$*-1$ on failure $($if setting the environment variable fails$).$

$*/$

int set$\_$env$\_$var$($const char $*$var$\_$name, const char $*$value$,$ int overwrite$)$

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