open_file, close_file, get_line, get_byte, put_byte, purge_stdin

open_file("filename"[,"mode"])

:: Opens filename for reading.

close_file(num)

:: Closes the file indicated by a descriptor num.

get_line([num])

:: Reads a line from the file indicated by a descriptor num.

get_byte(num)

:: Reads a byte from the file indicated by a descriptor num.

put_byte(num)

:: Writes a byte to the file indicated by a descriptor num.

purge_stdin()

purge_stdin()

:: Clears the buffer for the standard input.

return

open_file() : integer (fild id); close_file() : 1; get_line() : string; get_byte(), put_byte() : integer

filename

file (path) name

mode

string

num

non-negative integer (file descriptor)

• open_file() opens a file. If mode is not specified, a file is opened for reading. If mode is specified, it is used as the mode specification for C standard I/O function fopen(). For example "w" requests that the file is truncated to zero length or created for writing. "a" requests that the file is opened for writing or created if it does not exist. The stream pointer is set at the end of the file. If successful, it returns a non-negative integer as the file descriptor. Otherwise the system error function is called. Unnecessary files should be closed by close_file().
• get_line() reads a line from an opened file and returns the line as a string. If no argument is supplied, it reads a line from the standard input.
• get_byte() reads a byte from an opened file and returns the it as an integer.
• put_byte() writes a byte from an opened file and returns the the byte as an integer.
• A get_line() call after reading the end of file returns an integer 0.
• Strings can be converted into internal forms with string manipulation functions such as sub_str(), eval_str().
• purge_stdin() clears the buffer for the standard input. When a function receives a character string from get_line(), this functions should be called in advance in order to avoid an incorrect behavior which is caused by the characters already exists in the buffer.

[185] Id = open_file("test");
0
[186] get_line(Id);
12345

[187] get_line(Id);
67890

[188] get_line(Id);
0
[189] type(@@);
0
[190] close_file(Id);
1
[191] open_file("test");
1
[192] get_line(1);   
12345

[193] get_byte(1);
54                   /* the ASCII code of '6' */
[194] get_line(1);
7890                 /* the rest of the last line */
[195] def test() { return get_line(); }
[196] def test1() { purge_stdin(); return get_line(); }
[197] test();
                     /* a remaining newline character has been read */
                     /* returns immediately */
[198] test1();
123;                 /* input from a keyboard */
123;                 /* returned value */

[199] 

References

section eval_str, section str_len, str_chr, sub_str.

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