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Update README file.

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This commit is contained in:
Gregory Nutt 2018-08-11 08:21:52 -06:00
parent 516a743344
commit 5cfe9c2787
1 changed files with 45 additions and 25 deletions
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70
nshlib/README.txt
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@ -92,6 +92,14 @@ Command Overview
FLASH footprint results but then also only simple environment
variables like $FOO can be used on the command line.
CONFIG_NSH_QUOTE enables back-slash quoting of certain characters within
the command. This option is useful for the case where an NSH script is
used to dynamically generate a new NSH script. In that case, commands
must be treated as simple text strings without interpretation of any
special characters. Special characters such as $, `, ", and others must
be retained intact as part of the test string. This option is currently
only available is CONFIG_NSH_ARGCAT is also selected.
Conditional Command Execution
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -117,12 +125,15 @@ Looping
while [!] <test-cmd>; do <cmd-sequence>; done
Execute <cmd-sequence> as long as <test-cmd> has an exit status of
zero (OR nonzero if inverted with '!').
zero (OR non-zero if inverted with '!').
until [!] <test-cmd>; do <cmd-sequence>; done
Execute <cmd-sequence> as long as <test-cmd> has a non-zero exit
status (OR nonzero if inverted with '!').
status (OR zero if inverted with '!').
Note that 'while' is equivalent to 'until' if the command result is
inverted.
A break command is also supported. The break command is only meaningful
within the body of the a while or until loop, between the do and done
@ -1490,38 +1501,47 @@ NSH-Specific Configuration Settings
Default: n
* CONFIG_NSH_CMDPARMS
If selected, then the output from commands, from file applications, and
from NSH built-in commands can be used as arguments to other
commands. The entity to be executed is identified by enclosing the
command line in back quotes. For example,
If selected, then the output from commands, from file applications, and
from NSH built-in commands can be used as arguments to other
commands. The entity to be executed is identified by enclosing the
command line in back quotes. For example,
set FOO `myprogram $BAR`
set FOO `myprogram $BAR`
Will execute the program named myprogram passing it the value of the
environment variable BAR. The value of the environment variable FOO
is then set output of myprogram on stdout. Because this feature commits
significant resources, it is disabled by default.
Will execute the program named myprogram passing it the value of the
environment variable BAR. The value of the environment variable FOO
is then set output of myprogram on stdout. Because this feature commits
significant resources, it is disabled by default.
The CONFIG_NSH_CMDPARMS interim output will be retained in a temporary
file. Full path to a directory where temporary files can be created is
taken from CONFIG_LIBC_TMPDIR and it defaults to /tmp if
CONFIG_LIBC_TMPDIR is not set.
The CONFIG_NSH_CMDPARMS interim output will be retained in a temporary
file. Full path to a directory where temporary files can be created is
taken from CONFIG_LIBC_TMPDIR and it defaults to /tmp if
CONFIG_LIBC_TMPDIR is not set.
* CONFIG_NSH_MAXARGUMENTS
The maximum number of NSH command arguments. Default: 6
The maximum number of NSH command arguments. Default: 6
* CONFIG_NSH_ARGCAT
Support concatenation of strings with environment variables or command
output. For example:
Support concatenation of strings with environment variables or command
output. For example:
set FOO XYZ
set BAR 123
set FOOBAR ABC_${FOO}_${BAR}
set FOO XYZ
set BAR 123
set FOOBAR ABC_${FOO}_${BAR}
would set the environment variable FOO to XYZ, BAR to 123 and FOOBAR
to ABC_XYZ_123. If NSH_ARGCAT is not selected, then a slightly small
FLASH footprint results but then also only simple environment
variables like $FOO can be used on the command line.
would set the environment variable FOO to XYZ, BAR to 123 and FOOBAR
to ABC_XYZ_123. If NSH_ARGCAT is not selected, then a slightly small
FLASH footprint results but then also only simple environment
variables like $FOO can be used on the command line.
* CONFIG_NSH_QUOTE
Enables back-slash quoting of certain characters within the command.
This option is useful for the case where an NSH script is used to
dynamically generate a new NSH script. In that case, commands must
be treated as simple text strings without interpretation of any
special characters. Special characters such as $, `, ", and others
must be retained intact as part of the test string. This option is
currently only available is CONFIG_NSH_ARGCAT is also selected.
* CONFIG_NSH_NESTDEPTH
The maximum number of nested if-then[-else]-fi sequences that