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xv6-cs450
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formatting tweaks

This commit is contained in:
rsc 2007-08-28 03:46:58 +00:00
parent 2868ca0f37
commit a759b8a450
1 changed files with 66 additions and 55 deletions
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121
sh.c
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@ -49,19 +49,9 @@ struct backcmd {
struct cmd *cmd;
};
struct cmd *parsecmd(char*);
int fork1(void); // Fork but panics on failure.
void panic(char*);
int
fork1(void)
{
int pid;
pid = fork();
if(pid == -1)
panic("fork");
return pid;
}
struct cmd *parsecmd(char*);
// Execute cmd. Never returns.
void
@ -99,6 +89,14 @@ runcmd(struct cmd *cmd)
runcmd(rcmd->cmd);
break;
case LIST:
lcmd = (struct listcmd*)cmd;
if(fork1() == 0)
runcmd(lcmd->left);
wait();
runcmd(lcmd->right);
break;
case PIPE:
pcmd = (struct pipecmd*)cmd;
if(pipe(p) < 0)
@ -123,14 +121,6 @@ runcmd(struct cmd *cmd)
wait();
break;
case LIST:
lcmd = (struct listcmd*)cmd;
if(fork1() == 0)
runcmd(lcmd->left);
wait();
runcmd(lcmd->right);
break;
case BACK:
bcmd = (struct backcmd*)cmd;
if(fork1() == 0)
@ -155,7 +145,17 @@ int
main(void)
{
static char buf[100];
int fd;
// Assumes three file descriptors open.
while((fd = open("console", O_RDWR)) >= 0){
if(fd >= 3){
close(fd);
break;
}
}
// Read and run input commands.
while(getcmd(buf, sizeof(buf)) >= 0) {
if(fork1() == 0)
runcmd(parsecmd(buf));
@ -171,6 +171,18 @@ panic(char *s)
exit();
}
int
fork1(void)
{
int pid;
pid = fork();
if(pid == -1)
panic("fork");
return pid;
}
//PAGEBREAK!
// Constructors
struct cmd*
@ -237,24 +249,12 @@ backcmd(struct cmd *subcmd)
cmd->cmd = subcmd;
return (struct cmd*)cmd;
}
//PAGEBREAK!
// Parsing
char whitespace[] = " \t\r\n\v";
char symbols[] = "<|>&;()";
int
peek(char **ps, char *es, char *toks)
{
char *s;
s = *ps;
while(s < es && strchr(whitespace, *s))
s++;
*ps = s;
return *s && strchr(toks, *s);
}
int
gettoken(char **ps, char *es, char **q, char **eq)
{
@ -300,12 +300,22 @@ gettoken(char **ps, char *es, char **q, char **eq)
return ret;
}
void nulterminate(struct cmd*);
int
peek(char **ps, char *es, char *toks)
{
char *s;
s = *ps;
while(s < es && strchr(whitespace, *s))
s++;
*ps = s;
return *s && strchr(toks, *s);
}
struct cmd *parseline(char**, char*);
struct cmd *parsepipe(char**, char*);
struct cmd *parseredirs(struct cmd*, char**, char*);
struct cmd *parseblock(char**, char*);
struct cmd *parseexec(char**, char*);
struct cmd *nulterminate(struct cmd*);
struct cmd*
parsecmd(char *s)
@ -354,22 +364,6 @@ parsepipe(char **ps, char *es)
return cmd;
}
struct cmd*
parseblock(char **ps, char *es)
{
struct cmd *cmd;
if(!peek(ps, es, "("))
panic("parseblock");
gettoken(ps, es, 0, 0);
cmd = parseline(ps, es);
if(!peek(ps, es, ")"))
panic("syntax - missing )");
gettoken(ps, es, 0, 0);
cmd = parseredirs(cmd, ps, es);
return cmd;
}
struct cmd*
parseredirs(struct cmd *cmd, char **ps, char *es)
{
@ -395,6 +389,22 @@ parseredirs(struct cmd *cmd, char **ps, char *es)
return cmd;
}
struct cmd*
parseblock(char **ps, char *es)
{
struct cmd *cmd;
if(!peek(ps, es, "("))
panic("parseblock");
gettoken(ps, es, 0, 0);
cmd = parseline(ps, es);
if(!peek(ps, es, ")"))
panic("syntax - missing )");
gettoken(ps, es, 0, 0);
cmd = parseredirs(cmd, ps, es);
return cmd;
}
struct cmd*
parseexec(char **ps, char *es)
{
@ -429,7 +439,7 @@ parseexec(char **ps, char *es)
}
// NUL-terminate all the counted strings.
void
struct cmd:
nulterminate(struct cmd *cmd)
{
int i;
@ -440,7 +450,7 @@ nulterminate(struct cmd *cmd)
struct redircmd *rcmd;
if(cmd == 0)
return;
return 0;
switch(cmd->type){
case EXEC:
@ -472,4 +482,5 @@ nulterminate(struct cmd *cmd)
nulterminate(bcmd->cmd);
break;
}
return cmd;
}