Dear Andrew Ruder,
On 10/22/2013 05:07 PM, Andrew Ruder wrote:
env exists is a way to test (in hush) if an environment variable exists. A workaround existed using printenv but this new command doesn't require all the stdout/stderr redirection to prevent printing information to the screen.
I was aware of the printenv workaround, and have used it. I share your misgivings about the stdout/stderr redirection, it seems clumsy, at best.
I have, more recently, been using scripting of the form
if test "X" != "X${var}"; then echo defined else echo undefined fi
Example: $ set testexists 1 $ env exists testexists && echo "yes" yes $ env exists testexists || echo "no" $ set testexists $ env exists testexists && echo "yes" $ env exists testexists || echo "no" no $
I've often thought that a "env exists" command might be a nice, consistent, addition.
Thanks for adding it.
Jim
Signed-off-by: Andrew Ruder andrew.ruder@elecsyscorp.com
README | 1 + common/cmd_nvedit.c | 23 +++++++++++++++++++++++ 2 files changed, 24 insertions(+)
diff --git a/README b/README index 09662a4..0718459 100644 --- a/README +++ b/README @@ -843,6 +843,7 @@ The following options need to be configured: CONFIG_CMD_ELF * bootelf, bootvx CONFIG_CMD_ENV_CALLBACK * display details about env callbacks CONFIG_CMD_ENV_FLAGS * display details about env flags
CONFIG_CMD_ENV_EXISTS * check existence of env variablediff --git a/common/cmd_nvedit.c b/common/cmd_nvedit.c index ba9ba16..0d4d02c 100644 --- a/common/cmd_nvedit.c +++ b/common/cmd_nvedit.c @@ -1059,6 +1059,23 @@ sep_err: } #endif
+#if defined(CONFIG_CMD_ENV_EXISTS) +static int do_env_exists(cmd_tbl_t *cmdtp, int flag, int argc,
char * const argv[])+{
- ENTRY e, *ep;
- if (argc < 2)
return CMD_RET_USAGE;- e.key = argv[1];
- e.data = NULL;
- hsearch_r(e, FIND, &ep, &env_htab, 0);
- return (ep == NULL) ? 1 : 0;
+} +#endif
- /*
*/
- New command line interface: "env" command with subcommands
@@ -1094,6 +1111,9 @@ static cmd_tbl_t cmd_env_sub[] = { U_BOOT_CMD_MKENT(save, 1, 0, do_env_save, "", ""), #endif U_BOOT_CMD_MKENT(set, CONFIG_SYS_MAXARGS, 0, do_env_set, "", ""), +#if defined(CONFIG_CMD_ENV_EXISTS)
- U_BOOT_CMD_MKENT(exists, 2, 0, do_env_exists, "", ""),
+#endif };
#if defined(CONFIG_NEEDS_MANUAL_RELOC) @@ -1136,6 +1156,9 @@ static char env_help_text[] = #if defined(CONFIG_CMD_EDITENV) "env edit name - edit environment variable\n" #endif +#if defined(CONFIG_CMD_ENV_EXISTS)
- "env exists name - tests for existence of variable\n"
+#endif #if defined(CONFIG_CMD_EXPORTENV) "env export [-t | -b | -c] [-s size] addr [var ...] - export environment\n" #endif