.de sr .sp 1 .ft I .ne 2 \\$1 .if t .sp .2 .br .ft R .. .de it \fI\\$1\fR .. .TL A New Input-Output Package .AU D. M. Ritchie .PP A new package of IO routines is available. It was designed with the following goals in mind. .IP 1. It should be similar in spirit to the earlier Portable Library, and, to the extent possible, be compatible with it. At the same time a few dubious design choices in the Portable Library will be corrected. .IP 2. It must be as efficient as possible, both in time and in space, so that there will be no hesitation in using it no matter how critical the application. .IP 3. It must be simple to use, and also free of the magic numbers and mysterious calls the use of which mars the understandability and portability of many programs using older packages. .IP 4. The interface provided should be applicable on all machines, whether or not the programs which implement it are directly portable to other systems, or to machines other than the PDP11 running a version of Unix. .PP It is intended that this package replace the Portable Library. Although it is not directly compatible, as discussed below, it is sufficiently similar that a set of relatively small, inexpensive adaptor routines exist which make it appear identical to the current Portable Library except in some very obscure details. .PP The most crucial difference between this package and the Portable Library is that the current offering names streams in terms of pointers rather than by the integers known as `file descriptors.' Thus, for example, the routine which opens a named file returns a pointer to a certain structure rather than a number; the routine which reads an open file takes as an argument the pointer returned from the open call. .SH General Usage .PP Each program using the library must have the line .DS #include <stdio.h> .DE which defines certain macros and variables. The library containing the routines is `/usr/lib/libS.a,' so the command to compile is .DS cc . . . \-lS .DE All names in the include file intended only for internal use begin with an underscore `\_' to reduce the possibility of collision with a user name. The names intended to be visible outside the package are .IP stdin 10 The name of the standard input file .IP stdout 10 The name of the standard output file .IP stderr 10 The name of the standard error file .IP EOF 10 is actually \-1, and is the value returned by the read routines on end-of-file or error. .IP NULL 10 is a notation for the null pointer, returned by pointer-valued functions to indicate an error .IP FILE 10 expands to `struct \_iob' and is a useful shorthand when declaring pointers to streams. .IP BUFSIZ is a number (viz. 512) of the size suitable for an IO buffer supplied by the user. See .it setbuf, below. .IP "getc, getchar, putc, putchar, feof, ferror, fileno" 10 .br are defined as macros. Their actions are described below; they are mentioned here to point out that it is not possible to redeclare them and that they are not actually functions; thus, for example, they may not have breakpoints set on them. .PP The routines in this package, like the current Portable Library, offer the convenience of automatic buffer allocation and output flushing where appropriate. Absent, however, is the facility of changing the default input and output streams by assigning to `cin' and `cout.' The names `stdin,' stdout,' and `stderr' are in effect constants and may not be assigned to. .SH Calls .PP The routines in the library are in nearly one-to-one correspondence with those in the Portable Library. In several cases the name has been changed. This is an attempt to reduce confusion. If the attempt is judged to fail the names may be made identical even though the arguments may be different. The order of this list generally follows the order used in the Portable Library document. .sr "FILE *fopen(filename, type)" .br char *filename, *type; .br .it Fopen opens the file and, if needed, allocates a buffer for it. .it Filename is a character string specifying the name. .it Type is a character string (not a single character). It may be `"r",' `"w",' or `"a"' to indicate intent to read, write, or append. The value returned is a file pointer. If it is null the attempt to open failed. .sr "FILE *freopen(filename, type, ioptr) .br char *filename, *type; .br FILE *ioptr; .br The stream named by .it ioptr is closed, if necessary, and then reopened as if by .it fopen. If the attempt to open fails, NULL is returned, otherwise .it ioptr, which will now refer to the new file. .PP Often the reopened stream is .it stdin or .it stdout. .sr "int getc(ioptr)" returns the next character from the stream named by .it ioptr, which is a pointer to a file such as returned by .it fopen, or the name .it stdin. The integer EOF is returned on end-of-file or when an error occurs. The null character is a legal character. .sr "int fgetc(ioptr)" is identical in function to `getc' but is a genuine function, not a macro. .sr "putc(c, ioptr)" .it Putc writes the character .it c on the output stream named by .it ioptr, which is a value returned from .it fopen or perhaps .it stdout or .it stderr. The character is returned as value, but EOF is returned on error. .sr "fputc(c, ioptr) Fputc is identical in function to `putc' but is a genuine function, not a macro. .sr fclose(ioptr) The file corresponding to .it ioptr is closed after any buffers are emptied. A buffer allocated by the IO system is freed. .it Fclose is automatic on normal termination of the program. .sr fflush(ioptr) Any buffered information on the (output) stream named by .it ioptr is written out. Output files are normally buffered if and only if they are not directed to the terminal, but .it stderr is unbuffered unless .it setbuf is used. .sr exit(errcode) .it Exit terminates the process and returns its argument as status to the parent. This is a special version of the routine which calls .it fflush for each output file. To terminate without flushing, use .it \_exit. .sr feof(ioptr) returns non-zero when end-of-file has occurred on the specified input stream. .sr ferror(ioptr) returns non-zero when an error has occurred while reading or writing the named stream. The error indication lasts until the file has been closed. .sr "getchar( )" is identical to `getc(stdin)'. .sr "putchar(c)" is identical to `putc(c, stdout)'. .sr "char *gets(s)" reads characters up to a new-line from the standard input. The new-line character is replaced by a null character. It is the user's responsibility to make sure that the character array .it s is large enough. .it Gets returns its argument, or null if end-of-file or error occurred. Note that this routine is not compatible with .it fgets; it is included for downward compatibility. .sr "char *fgets(s, n, ioptr)" reads up to .it n characters from the stream .it ioptr into the character pointer .it s. The read terminates with a new-line character. The new-line character is placed in the buffer followed by a null pointer. The first argument, or a null pointer if error or end-of-file occurred, is returned. .sr puts(s) writes the null-terminated string (character array) .it s on the standard output. A new-line is appended. No value is returned. Note that this routine is not compatible with .it fputs; it is included for downward compatibility. .sr "fputs(s, ioptr)" writes the null-terminated string (character array) on the stream .it s. No new-line is appended. No value is returned. .sr "ungetc(c, ioptr)" The argument character .it c is pushed back on the input stream named by .it ioptr. Only one character may be pushed back. .sr "printf(format, a1, . . .)" .sr "fprintf(ioptr, format, a