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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
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