Part 8 — File and I/O Operations¶

8.1 I/O Overview¶

The Heirloom PL/I Runtime supports both stream-oriented and record-oriented I/O, preserving the semantics of mainframe PL/I file processing.

8.1.1 I/O Architecture¶

┌─────────────────────────────────────────────┐
│               PL/I I/O Layer                │
│                                             │
│  ┌─────────────────┐  ┌─────────────────┐  │
│  │ Stream I/O      │  │ Record I/O      │  │
│  │ (PLIStream)     │  │ (PLIRecord)     │  │
│  │                 │  │                 │  │
│  │ GET LIST        │  │ READ            │  │
│  │ GET EDIT        │  │ WRITE           │  │
│  │ GET DATA        │  │ REWRITE         │  │
│  │ PUT LIST        │  │ LOCATE          │  │
│  │ PUT EDIT        │  │ NOTE            │  │
│  │ PUT DATA        │  │                 │  │
│  │ PUT STRING      │  │ ISAM support    │  │
│  │ GET STRING      │  │ Sequential      │  │
│  │                 │  │ Direct/random   │  │
│  └────────┬────────┘  └────────┬────────┘  │
│           │                    │            │
│           └────────┬───────────┘            │
│                    ▼                        │
│           ┌─────────────────┐               │
│           │ PLIFile Factory │               │
│           │ (IPLIFile)      │               │
│           │                 │               │
│           │ DD name mapping │               │
│           │ Env. variables  │               │
│           │ Properties      │               │
│           └─────────────────┘               │
└─────────────────────────────────────────────┘

8.2 File Declaration and Attributes¶

8.2.1 FILE Declaration¶

DCL MYFILE FILE RECORD INPUT SEQUENTIAL ENV(F RECSIZE(80));
DCL REPORT FILE STREAM OUTPUT PRINT;

8.2.2 File Attributes¶

8.3 File Operations¶

8.3.1 OPEN Statement¶

Open a file with specified attributes.

8.3.2 CLOSE Statement¶

Close one or more open files.

8.3.3 DD Name Resolution¶

Files are resolved via environment variables in the following order: 1. DD_<filename> environment variable 2. DDNAME_<filename> environment variable 3. Property file configuration 4. Direct file path

8.4 Stream I/O¶

8.4.1 GET LIST¶

Read data items separated by blanks or commas.

8.4.2 GET EDIT¶

Read data items with format-directed editing.

8.4.3 GET DATA¶

Read self-identifying data (name=value pairs).

8.4.4 PUT LIST¶

Write data items in default format.

8.4.5 PUT EDIT¶

Write data items with format-directed editing.

Format items: A(w), F(w,d), E(w,d,s), B(w), P'picture', X(n), SKIP(n), COLUMN(n), PAGE, LINE(n)

8.4.6 PUT DATA¶

Write self-identifying data.

8.4.7 PUT STRING / GET STRING¶

In-memory stream I/O using character strings as source/target.

8.5 Record I/O¶

8.5.1 READ Statement¶

Read a record from a file.

Options: FILE, INTO, SET, KEY, KEYTO, IGNORE

8.5.2 WRITE Statement¶

Write a record to a file.

Options: FILE, FROM, KEYFROM

8.5.3 REWRITE Statement¶

Rewrite a record in place.

Options: FILE, FROM, KEY

8.5.4 LOCATE Statement¶

Locate-mode output (allocate buffer, write on next I/O).

8.5.5 NOTE Statement¶

Get the current file position.

8.5.6 FLUSH Statement¶

Flush output buffers.

8.6 Print File Support¶

8.6.1 PRINT Attribute¶

• SYSPRINT as default print file
• Page control (PAGE, SKIP, LINE, COLUMN)
• Automatic pagination

8.6.2 ENDPAGE Condition¶

Raised when output reaches the end of a page.