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[cmdline] Add setting expansion using ${...} syntax
Allow settings to be expanded in arbitrary commands, such as

  kernel http://10.0.0.1/boot.php?uuid=${uuid}

Also add the "echo" command, as being the easiest way to test this
features.
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Michael Brown committed Jul 27, 2008
1 parent 702e0be commit 34a06b6
Showing 1 changed file with 96 additions and 2 deletions.
98 changes: 96 additions & 2 deletions src/core/exec.c
Expand Up @@ -26,6 +26,7 @@
#include <assert.h>
#include <gpxe/tables.h>
#include <gpxe/command.h>
#include <gpxe/settings.h>

/** @file
*
Expand Down Expand Up @@ -86,6 +87,76 @@ int execv ( const char *command, char * const argv[] ) {
return -ENOEXEC;
}

/**
* Expand variables within command line
*
* @v command Command line
* @ret expcmd Expanded command line
*
* The expanded command line is allocated with malloc() and the caller
* must eventually free() it.
*/
static char * expand_command ( const char *command ) {
char *expcmd;
char *start;
char *end;
char *head;
char *name;
char *tail;
int setting_len;
int new_len;
char *tmp;

/* Obtain temporary modifiable copy of command line */
expcmd = strdup ( command );
if ( ! expcmd )
return NULL;

/* Expand while expansions remain */
while ( 1 ) {

head = expcmd;

/* Locate opener */
start = strstr ( expcmd, "${" );
if ( ! start )
break;
*start = '\0';
name = ( start + 2 );

/* Locate closer */
end = strstr ( name, "}" );
if ( ! end )
break;
*end = '\0';
tail = ( end + 1 );

/* Determine setting length */
setting_len = fetchf_named_setting ( name, NULL, 0 );
if ( setting_len < 0 )
setting_len = 0; /* Treat error as empty setting */

/* Read setting into temporary buffer */
{
char setting_buf[ setting_len + 1 ];

setting_buf[0] = '\0';
fetchf_named_setting ( name, setting_buf,
sizeof ( setting_buf ) );

/* Construct expanded string and discard old string */
tmp = expcmd;
new_len = asprintf ( &expcmd, "%s%s%s",
head, setting_buf, tail );
free ( tmp );
if ( new_len < 0 )
return NULL;
}
}

return expcmd;
}

/**
* Split command line into argv array
*
Expand Down Expand Up @@ -135,8 +206,8 @@ int system ( const char *command ) {
int argc;
int rc = 0;

/* Obtain temporary modifiable copy of command line */
args = strdup ( command );
/* Perform variable expansion */
args = expand_command ( command );
if ( ! args )
return -ENOMEM;

Expand All @@ -157,3 +228,26 @@ int system ( const char *command ) {
free ( args );
return rc;
}

/**
* The "echo" command
*
* @v argc Argument count
* @v argv Argument list
* @ret rc Exit code
*/
static int echo_exec ( int argc, char **argv ) {
int i;

for ( i = 1 ; i < argc ; i++ ) {
printf ( "%s%s", ( ( i == 1 ) ? "" : " " ), argv[i] );
}
printf ( "\n" );
return 0;
}

/** "echo" command */
struct command echo_command __command = {
.name = "echo",
.exec = echo_exec,
};

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