Second drop. More infrastructure in place, especially for parsing pipelines.
The minimal version got a couple hundred bytes bigger, partly because it's broken into more functions but mostly because it now dynamically reallocates and frees everything with no hard-coded limits. (I thought about making that optional, but there's a limit to what I can debug and maintain. It should still be reasonably NOMMU friendly, the allocations are small and short lived, and shouldn't contribute noticeably to long-term memory fragmentation.)
This commit is contained in:
Rob Landley
parent
c27f4f5445
commit
3476ad651d
195
shell/bbsh.c
195
shell/bbsh.c
@ -7,49 +7,197 @@
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* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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*/
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// Handle embedded NUL bytes in the command line.
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// A section of code that gets repeatedly or conditionally executed is stored
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// as a string and parsed each time it's run.
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// Wheee, debugging.
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// Terminal control
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#define ENABLE_BBSH_TTY 0
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// &, fg, bg, jobs. (ctrl-z with tty.)
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#define ENABLE_BBSH_JOBCTL 0
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// Flow control (if, while, for, functions { })
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#define ENABLE_BBSH_FLOWCTL 0
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#define ENABLE_BBSH_ENVVARS 0 // Environment variable support
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// Local and synthetic variables, fancy prompts, set, $?, etc.
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#define ENABLE_BBSH_LOCALVARS 0
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// Pipes and redirects: | > < >> << && || & () ;
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#define ENABLE_BBSH_PIPES 0
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/* Fun:
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echo `echo hello#comment " woot` and more
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*/
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#include <busybox.h>
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static int handle(char *command)
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// A single executable, its arguments, and other information we know about it.
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#define BBSH_FLAG_EXIT 1
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#define BBSH_FLAG_SUSPEND 2
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#define BBSH_FLAG_PIPE 4
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#define BBSH_FLAG_AND 8
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#define BBSH_FLAG_OR 16
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#define BBSH_FLAG_AMP 32
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#define BBSH_FLAG_SEMI 64
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#define BBSH_FLAG_PAREN 128
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// What we know about a single process.
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struct command {
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struct command *next;
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int flags; // exit, suspend, && ||
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int pid; // pid (or exit code)
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int argc;
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char *argv[0];
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};
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// A collection of processes piped into/waiting on each other.
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struct pipeline {
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struct pipeline *next;
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int job_id;
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struct command *cmd;
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char *cmdline;
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int cmdlinelen;
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};
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static void free_list(void *list, void (*freeit)(void *data))
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{
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int argc=0;
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char *argv[10], *start = command;
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while(list) {
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void **next = (void **)list;
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void *list_next = *next;
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freeit(list);
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free(list);
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list = list_next;
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}
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}
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// Parse one word from the command line, appending one or more argv[] entries
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// to struct command. Handles environment variable substitution and
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// substrings. Returns pointer to next used byte, or NULL if it
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// hit an ending token.
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static char *parse_word(char *start, struct command **cmd)
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{
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char *end;
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// Detect end of line (and truncate line at comment)
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if (ENABLE_BBSH_PIPES && strchr("><&|(;", *start)) return 0;
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// Grab next word. (Add dequote and envvar logic here)
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end = start;
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while (*end && !isspace(*end)) end++;
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(*cmd)->argv[(*cmd)->argc++] = xstrndup(start, end-start);
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// Allocate more space if there's no room for NULL terminator.
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if (!((*cmd)->argc & 7))
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*cmd = xrealloc(*cmd,
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sizeof(struct command) + ((*cmd)->argc+8)*sizeof(char *));
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(*cmd)->argv[(*cmd)->argc] = 0;
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return end;
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}
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// Parse a line of text into a pipeline.
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// Returns a pointer to the next line.
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static char *parse_pipeline(char *cmdline, struct pipeline *pipe)
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{
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struct command **cmd = &(pipe->cmd);
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char *start = pipe->cmdline = cmdline;
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if (!cmdline) return 0;
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if (ENABLE_BBSH_JOBCTL) pipe->cmdline = cmdline;
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// Parse command into argv[]
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for (;;) {
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char *end;
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// Skip leading whitespace and detect EOL.
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while(isspace(*start)) start++;
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if(!*start || *start=='#') break;
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// Grab next word. (Add dequote and envvar logic here)
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end=start;
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while(*end && !isspace(*end)) end++;
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argv[argc++]=xstrndup(start,end-start);
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start=end;
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// Skip leading whitespace and detect end of line.
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while (isspace(*start)) start++;
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if (!*start || *start=='#') {
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if (ENABLE_BBSH_JOBCTL) pipe->cmdlinelen = start-cmdline;
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return 0;
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}
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argv[argc]=0;
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if (!argc) return 0;
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if (argc==2 && !strcmp(argv[0],"cd")) chdir(argv[1]);
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else if(!strcmp(argv[0],"exit")) exit(argc>1 ? atoi(argv[1]) : 0);
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// Allocate next command structure if necessary
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if (!*cmd) *cmd = xzalloc(sizeof(struct command)+8*sizeof(char *));
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// Parse next argument and add the results to argv[]
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end = parse_word(start, cmd);
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// If we hit the end of this command, how did it end?
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if (!end) {
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if (ENABLE_BBSH_PIPES && *start) {
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if (*start==';') {
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start++;
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break;
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}
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// handle | & < > >> << || &&
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}
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break;
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}
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start = end;
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}
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if (ENABLE_BBSH_JOBCTL) pipe->cmdlinelen = start-cmdline;
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return start;
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}
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// Execute the commands in a pipeline
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static int run_pipeline(struct pipeline *pipe)
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{
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struct command *cmd = pipe->cmd;
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if (!cmd || !cmd->argc) return 0;
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// Handle local commands. This is totally fake and plastic.
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if (cmd->argc==2 && !strcmp(cmd->argv[0],"cd"))
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chdir(cmd->argv[1]);
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else if(!strcmp(cmd->argv[0],"exit"))
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exit(cmd->argc>1 ? atoi(cmd->argv[1]) : 0);
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else {
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int status;
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pid_t pid=fork();
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if(!pid) {
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run_applet_by_name(argv[0],argc,argv);
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execvp(argv[0],argv);
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printf("No %s",argv[0]);
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run_applet_by_name(cmd->argv[0],cmd->argc,cmd->argv);
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execvp(cmd->argv[0],cmd->argv);
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printf("No %s",cmd->argv[0]);
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exit(1);
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} else waitpid(pid, &status, 0);
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}
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while(argc) free(argv[--argc]);
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return 0;
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}
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static void free_cmd(void *data)
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{
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struct command *cmd=(struct command *)data;
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while(cmd->argc) free(cmd->argv[--cmd->argc]);
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}
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static void handle(char *command)
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{
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struct pipeline pipe;
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char *start = command;
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for (;;) {
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memset(&pipe,0,sizeof(struct pipeline));
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start = parse_pipeline(start, &pipe);
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if (!pipe.cmd) break;
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run_pipeline(&pipe);
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free_list(pipe.cmd, free_cmd);
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}
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}
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int bbsh_main(int argc, char *argv[])
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{
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char *command=NULL;
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@ -62,8 +210,11 @@ int bbsh_main(int argc, char *argv[])
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else {
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unsigned cmdlen=0;
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for (;;) {
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struct pipeline pipe;
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if(!f) putchar('$');
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if(1 > getline(&command,&cmdlen,f ? : stdin)) break;
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if(1 > getline(&command, &cmdlen,f ? : stdin)) break;
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handle(command);
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}
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if (ENABLE_FEATURE_CLEAN_UP) free(command);
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