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- .. SPDX-License-Identifier: GPL-2.0+
- Command-line Parsing
- ====================
- The command line is available in U-Boot proper, enabled by CONFIG_CMDLINE which
- is on by default. It is not enabled in SPL.
- There are two different command-line parsers available with U-Boot:
- the old "simple" one, and the much more powerful "hush" shell:
- Simple command-line parser
- --------------------------
- This takes very little code space and offers only basic features:
- - supports environment variables (through setenv / saveenv commands)
- - several commands on one line, separated by ';'
- - variable substitution using "... ${name} ..." syntax
- - special characters ('$', ';') can be escaped by prefixing with '\',
- for example::
- setenv bootcmd bootm \${address}
- - You can also escape text by enclosing in single apostrophes, for example::
- setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
- Hush shell
- ----------
- This is similar to Bourne shell, with control structures like:
- - `if`... `then` ... `else`... `fi`
- - `for`... `do` ... `done`
- - `while` ... `do` ... `done`
- - `until` ... `do` ... `done`
- Hush supports environment ("global") variables (through setenv / saveenv
- commands) and local shell variables (through standard shell syntax
- `name=value`); only environment variables can be used with the "run" command
- The Hush shell is enabled with `CONFIG_HUSH_PARSER`.
- General rules
- -------------
- #. If a command line (or an environment variable executed by a "run"
- command) contains several commands separated by semicolon, and
- one of these commands fails, then the remaining commands will be
- executed anyway.
- #. If you execute several variables with one call to run (i. e.
- calling run with a list of variables as arguments), any failing
- command will cause "run" to terminate, i. e. the remaining
- variables are not executed.
- Representing numbers
- --------------------
- Most U-Boot commands use hexadecimal (hex) as the default base, for convenient
- use of addresses, for example::
- => md 1000 6
- 00001000: 2c786f62 00697073 03000000 0c000000 box,spi.........
- 00001010: 67020000 00000000 ...g....
- There is no need to add a `0x` prefix to the arguments and the output is shown
- in hex also, without any prefixes. This helps to avoid clutter.
- Some commands use decimal where it is more natural::
- => i2c dev 0
- Setting bus to 0
- => i2c speed
- Current bus speed=400000
- => i2c speed 100000
- Setting bus speed to 100000 Hz
- In some cases the default is decimal but it is possible to use octal if that is
- useful::
- pmic dev pmic@41
- dev: 1 @ pmic@41
- => pmic write 2 0177
- => pmic read 2
- 0x02: 0x00007f
- It is possible to use a `0x` prefix to use a hex value if that is more
- convenient::
- => i2c speed 0x30000
- Setting bus speed to 196608 Hz
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