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