Saving and loading a text file.

load.c

#if !__STDC__ || __STDC_VERSION__ < 199901L
# error "This code is written in standard C99."
#else
# include <stdio.h> /* f(close|error|open|read)|size_t */

static signed int xTest_( const size_t Charge, const size_t Budget, char Text[ const restrict static Budget ] ) { return Budget <= Charge || ( Charge[ Text ] = 0 ); }

extern _Bool uLoad_( const size_t Length, char Text[ const restrict static Length ], const char Path[ const restrict static 1U ] )
{
	auto const char Mode[ ] = { "r" };
	auto FILE *const File = fopen( Path, Mode );

	auto signed int Flag = !File;

	switch( Flag )
	{
	case 0:
		Flag|= xTest_( fread( Text, sizeof *Text, Length, File ), Length, Text );
		Flag|= ferror( File );
		Flag|= fclose( File );

	default:
		return !Flag;
	}
}

#endif

save.c

#if !__STDC__ || __STDC_VERSION__ < 199901L
# error "This code is written in standard C99."
#else
# include <stdio.h> /* f(close|open|write)|size_t */
# include <string.h> /* size_t|strlen */

extern _Bool uSave_( const char Path[ const restrict static 1U ], const char Text[ const restrict static 1U ] )
{
	auto const size_t Length = strlen( Text );

	auto const char Mode[ ] = { "w" };
	auto FILE *const File = fopen( Path, Mode );

	auto signed int Flag = !File;

	switch( Flag )
	{
	case 0:
		Flag|= fwrite( Text, sizeof *Text, Length, File ) != Length;
		Flag|= fclose( File );

	default:
		return !Flag;
	}
}

#endif

test.c

#if !__STDC__ || __STDC_VERSION__ < 199901L
# error "This code is written in standard C99."
#else
# include <stdlib.h> /* EXIT_(FAILURE|SUCCESS) */
# include <string.h> /* strcmp */

extern signed int main( void )
{
	extern _Bool
		uLoad_( const size_t Length, char Text[ const restrict static Length ], const char Path[ const restrict static 1U ] ),
		uSave_( const char Path[ const restrict static 1U ], const char Text[ const restrict static 1U ] );

	auto const char
		Path[ ] = { "example.txt" },
		Source[ ] = { "I am a banana!\n" };
	auto char Target[ sizeof Source / sizeof *Source ] = { "" };

	return
		uSave_( Path, Source ) &&
		uLoad_( sizeof Target / sizeof *Target, Target, Path ) &&

		!strcmp( Source, Target )?

		EXIT_SUCCESS:
		EXIT_FAILURE;
}

#endif