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Take this part of the README and put it into rST format. Signed-off-by: Simon Glass <sjg@chromium.org>
56 lines
1.9 KiB
ReStructuredText
56 lines
1.9 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 setenv / saveenv commands)
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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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