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Update a README/Improve some C comments.

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This commit is contained in:
Gregory Nutt 2018-10-02 06:53:16 -06:00
parent 65e0b791b7
commit 8b01ea4434
2 changed files with 41 additions and 17 deletions
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49
nshlib/README.txt
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@ -520,25 +520,32 @@ o export <name> [<value>]
1. Using 'export' to promote an NSH variable to an environment variable. 1. Using 'export' to promote an NSH variable to an environment variable.
nsh> env nsh> env
PATH=/bin PATH=/bin
nsh> set foo bar nsh> set foo bar
nsh> env nsh> env
PATH=/bin PATH=/bin
nsh> export foo nsh> export foo
nsh> env nsh> env
PATH=/bin PATH=/bin
foo=bar foo=bar
A group-wide environment variable is created with the same value as the
local NSH variable; the local NSH variable is removed.
NOTE: This behavior differs from the Bash shell. Bash will retain the
local Bash variable which will shadow the environment variable of the
same name.
2. Using 'export' to set an environment variable 2. Using 'export' to set an environment variable
nsh> export dog poop nsh> export dog poop
nsh> env nsh> env
PATH=/bin PATH=/bin
foo=bar foo=bar
dog=poop dog=poop
The export command is not supported by NSH unless both CONFIG_NSH_VARS=y The export command is not supported by NSH unless both CONFIG_NSH_VARS=y
and CONFIG_DISABLE_ENVIRON is not set. and CONFIG_DISABLE_ENVIRON is not set.
@ -1116,8 +1123,18 @@ o set [{+|-}{e|x|xe|ex}] [<name> <value>]
foovalue foovalue
nsh> nsh>
If CONFIG_NSH_VARS is set, the effect of this 'set' command is to set the local If CONFIG_NSH_VARS is selected, the effect of this 'set' command is to set
NSH variable. Otherwise, the group-wide environment variable will be set. the local NSH variable. Otherwise, the group-wide environment variable
will be set.
If the local NSH variable has already been 'promoted' to an environment
variable, then the 'set' command will set the value of the environment
variable rather than the local NSH variable.
NOTE: The Bash shell does not work this way. Bash would set the value of
the local Bash variable and would not modify the environment variable.
The local Bash variable would that then shadow the environment variable
with a differing value.
Set the 'exit on error control' and/or 'print a trace' of commands when parsing Set the 'exit on error control' and/or 'print a trace' of commands when parsing
scripts in NSH. The settinngs are in effect from the point of exection, until scripts in NSH. The settinngs are in effect from the point of exection, until

9
nshlib/nsh_envcmds.c
View File

@ -411,6 +411,9 @@ int cmd_set(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
#ifndef CONFIG_DISABLE_ENVIRON #ifndef CONFIG_DISABLE_ENVIRON
/* Check if the NSH variable has already been promoted to an group- /* Check if the NSH variable has already been promoted to an group-
* wide environment variable. * wide environment variable.
*
* REVISIT: Is this the correct behavior? Bash would create/modify
* a local variable that shadows the environment variable.
*/ */
oldvalue = getenv(argv[ndx]); oldvalue = getenv(argv[ndx]);
@ -529,7 +532,11 @@ int cmd_export(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
} }
else else
{ {
/* Unset NSH variable */ /* Unset NSH variable.
*
* REVISIT: Is this the correct behavior? Bash would retain
* a local variable that shadows the environment variable.
*/
status = nsh_unsetvar(vtbl, argv[1]); status = nsh_unsetvar(vtbl, argv[1]);
if (status < 0 && status != -ENOENT) if (status < 0 && status != -ENOENT)