Chapter 6: Run IOCs with iocsh.bash

Run an Input/Output Controller (IOC) using installed module support without compiling an application binary. The iocsh.bash loader resolves module dependencies, loads shared libraries and database definition (DBD) files, and starts softIocPVX with your startup configuration.

Complete Chapter 1 first. Lessons 6.2 and 6.3 reuse the simulator scripts, databases, protocols, and fragments created in Chapters 3 and 4.

• Run an IOC with installed modules: inspect iocsh.bash -n output, load busy, and verify Channel Access (CA) and pvAccess (PVA) access.
• Connect the TCP simulator: run single-device and three-device StreamDevice startups by reusing training_device.iocsh unchanged.
• Read 32 temperature channels: load TC-32.db and expose a composite QSRV2 group process variable (PV) with dbLoadGroup.
• Add host statistics, autosave, and regex search: combine linStat, autosave, and retools with commonIocsh to persist a setpoint across restarts.
• Module selection and loader errors: pin module versions, check exported macros in cfg/iocsh.conf, and reproduce four startup error checks.

iocsh.bash loads installed record and device support. Application-specific C or C++ code requires a compiled IOC application as shown in Chapters 2 through 5.

Chapter exercises

1. In lesson 6.3, add a ch08 scalar mapping for $(P)$(R)CH08.VAL to tc32_group.json. Stop tc32_emulator.bash in terminal 1 with Ctrl+C, enter exit in terminal 2, start ./tc32_emulator.bash --port 9399 again in terminal 1, and restart iocsh.bash st.cmd in terminal 2. Confirm that pvxgl(1, "*") reports Atomic Members:5 and pvxget LOADER:TC32:Summary includes ch08.value.
2. In lesson 6.4, add a second ao record named $(P)Limit with field(PINI, "YES") and info(autosaveFields, "VAL"). Write a value with caput, wait 6 seconds, restart the IOC, and verify that settings.sav restores both records.
3. Run iocsh.bash -n on st.cmd from lesson 6.4 and explain why commonIocsh fragments (linStat.iocsh and autosave.iocsh) use iocshLoad rather than module directives.

Before moving on

• Every iocsh.bash (softIocPVX) session is stopped with exit.
• Every tcpserver.bash and tc32_emulator.bash process is stopped with Ctrl+C.
• ss -ltn 'sport = :9399 or sport = :9400 or sport = :9401' reports no active TCP listeners.
• Temporary scratch directories from lessons 6.1 and 6.5 are removed or noted outside the EPICS distribution tree.