Termux System

Termux System — Scheduling, IR, USB, NFC & Keystore

System-level automation and hardware interfaces from the command line via Termux API.

Important: Permission Handling

When a Termux API command runs for the first time, Android may prompt the user to grant permission. The command will fail with a permission/access error, but the user sees an approval dialog on their device. Always retry the command once if you get a permission error — the user will have approved the permission by then, and the retry will succeed.

Do not assume you lack access after a single permission failure. One retry is all it takes.

Quick Reference

Detailed Usage

termux-job-scheduler

Schedule scripts to run at a later time or on a recurring basis, optionally requiring network or charging.

termux-job-scheduler --script /sdcard/ruuh/backup.sh       # run once
termux-job-scheduler --script /sdcard/ruuh/sync.sh \
    --job-id 1 --period-ms 3600000                        # every hour
termux-job-scheduler --script /sdcard/ruuh/sync.sh \
    --job-id 2 --period-ms 86400000 --network unmetered \
    --charging true --persisted true                       # daily on WiFi while charging
termux-job-scheduler --pending                             # list pending jobs
termux-job-scheduler --cancel 1                            # cancel job by ID
termux-job-scheduler --cancel-all                          # cancel all jobs

Flags:

• --script <path> — path to script to execute
• --job-id <id> — integer job identifier (for cancel/update)
• --period-ms <ms> — repeat interval in milliseconds (0 = run once)
• --network <type> — required network: any, unmetered, none (default: any)
• --charging <bool> — require device charging: true or false (default: false)
• --persisted <bool> — survive reboots: true or false (default: false)
• --pending — list all pending scheduled jobs
• --cancel <id> — cancel a specific job by ID
• --cancel-all — cancel all scheduled jobs

termux-infrared-frequencies

Query the supported carrier frequency ranges of the device's IR transmitter.

termux-infrared-frequencies

[
  {"min": 30000, "max": 30000},
  {"min": 33000, "max": 33000},
  {"min": 36000, "max": 36000},
  {"min": 38000, "max": 38000},
  {"min": 40000, "max": 40000},
  {"min": 56000, "max": 56000}
]

Returns an array of objects with min and max frequency in Hz. An empty array means no IR transmitter is available.

termux-infrared-transmit

Transmit an IR pattern at a given carrier frequency.

termux-infrared-transmit -f 38000 9000,4500,560,560,560,1690,560,560,560,65535

Flags:

• -f <hz> — carrier frequency in Hz (e.g. 38000 for most consumer IR)

The positional argument is a comma-separated list of on/off durations in microseconds. The first value is "on", the second is "off", alternating. These patterns are specific to the target device's IR protocol (NEC, Samsung, Sony, etc.).

termux-usb

List or access USB devices connected to the Android device.

termux-usb -l                          # list connected USB devices
termux-usb -r /dev/bus/usb/001/002     # request permission for a device
termux-usb -e "cat" /dev/bus/usb/001/002  # run command with device fd
termux-usb -E /dev/bus/usb/001/002     # print device info

Flags:

• -l — list connected USB device paths
• -r <device> — request permission to access a USB device
• -e <command> — execute a command with the device file descriptor passed via env
• -E <device> — print USB device information (vendor/product IDs, class, etc.)

["/dev/bus/usb/001/002", "/dev/bus/usb/001/003"]

termux-nfc

Read from or write to NFC tags. The command waits for a tag to be tapped.

termux-nfc -r                          # read tag (wait for tap)
termux-nfc -w -t text "Hello NFC"      # write text record
termux-nfc -w -t url "https://example.com"  # write URL record

Flags:

• -r — read mode: wait for tag tap and return contents
• -w — write mode: wait for tag tap and write data
• -t <type> — NDEF record type for writing: text or url

Read output:

{
  "type": "NDEF",
  "records": [
    {
      "type": "text",
      "payload": "Hello NFC"
    }
  ]
}

termux-keystore

Hardware-backed cryptographic key management using Android Keystore. Keys never leave the secure hardware.

termux-keystore list                           # list stored keys
termux-keystore generate "mykey" -a RSA -s 2048  # generate RSA-2048 key
termux-keystore generate "ec256" -a EC -s 256    # generate EC P-256 key
termux-keystore sign "mykey" < data.bin > sig.bin  # sign data
termux-keystore verify "mykey" -s sig.bin < data.bin  # verify signature
termux-keystore delete "mykey"                 # delete a key

Subcommands:

• list — list all keys in the keystore
• generate <alias> — generate a new key pair
  • -a <algorithm> — RSA or EC
  • -s <size> — key size: 2048, 4096 for RSA; 256 for EC
• sign <alias> — sign data from stdin, output signature to stdout
• verify <alias> — verify a signature against data
  • -s <signature-file> — path to the signature file
• delete <alias> — delete a key from the keystore

["mykey", "ec256", "backup-signing-key"]

Common Patterns

Periodic backup on WiFi

# Create backup script
cat > /sdcard/ruuh/backup.sh << 'SCRIPT'
#!/bin/bash
tar czf "/sdcard/ruuh/backup-$(date +%Y%m%d).tar.gz" /sdcard/ruuh/MEMORY.md /sdcard/ruuh/AGENTS.md
SCRIPT
chmod +x /sdcard/ruuh/backup.sh

# Schedule daily on WiFi
termux-job-scheduler --script /sdcard/ruuh/backup.sh \
    --job-id 10 --period-ms 86400000 --network unmetered --persisted true

TV power toggle via IR

# Check IR is available
FREQS=$(termux-infrared-frequencies)
if [ "$FREQS" = "[]" ]; then
  echo "No IR transmitter on this device"
  exit 1
fi

# Samsung TV power toggle (NEC protocol, 38kHz)
termux-infrared-transmit -f 38000 \
    9000,4500,560,560,560,560,560,1690,560,1690,560,560,560,560,560,560,560,560,560,1690,560,1690,560,560,560,560,560,1690,560,1690,560,1690,560,1690,560,560,560,1690,560,560,560,560,560,560,560,560,560,560,560,560,560,1690,560,560,560,1690,560,1690,560,1690,560,1690,560,1690,560,1690,560,65535

NFC tap automation

# Read an NFC tag and act on contents
TAG=$(termux-nfc -r)
TYPE=$(echo "$TAG" | jq -r '.records[0].type')
PAYLOAD=$(echo "$TAG" | jq -r '.records[0].payload')

case "$TYPE" in
  url)
    termux-open-url "$PAYLOAD"
    ;;
  text)
    termux-toast "NFC: $PAYLOAD"
    ;;
esac

Sign a file with hardware key

# One-time: generate a signing key
termux-keystore generate "file-signer" -a EC -s 256

# Sign a file
termux-keystore sign "file-signer" < /sdcard/ruuh/release.tar.gz > /sdcard/ruuh/release.sig
termux-toast "File signed"

# Verify later
termux-keystore verify "file-signer" -s /sdcard/ruuh/release.sig < /sdcard/ruuh/release.tar.gz
echo "Signature valid: $?"