/*
* libexec.c
*
* Small wrapper for execve()
*
* (c) 2024 Dario Rodriguez <antartica@whereismybit.com>
* This file is in the public domain.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#ifndef FIONREAD
#include <sys/filio.h>
#endif
#include <stdarg.h>
#include "libexec.h"
#ifndef RD
#define RD 0
#endif
#ifndef WR
#define WR 1
#endif
exec_t *
exec_init(char *name, char *cmdwithstringsub, char **envp)
{
exec_t *exec;
char *ptr;
int n;
if((exec=malloc(sizeof(exec_t)))==NULL)
return(NULL); /* insuf. mem. */
memset(exec,0,sizeof(exec_t));
exec->pid=-1;
exec->laststatus=-1;
exec->fdin=exec->fdout=exec->fderr=-1;
exec->envp=envp;
if(name!=NULL && (exec->name=strdup(name))==NULL) {
exec_free(exec),exec=NULL;
return(NULL); /* insuf. mem. */
}
for(ptr=strchr(cmdwithstringsub,'%')
;ptr!=NULL && ptr[1]=='s'
;ptr=strchr(ptr+1,'%')
) {
for(n=0;(ptr-(n+1))>=cmdwithstringsub && ptr[-(n+1)]=='%';) {
n++;
}
if(((n+1)%2)==0)
continue; /* this '%' is escaped (duplicated) */
break; /* found the first %s */
}
exec->has_param=(ptr!=NULL)?1:0;
if(!(exec->has_param)) {
exec->prebuf=strdup(cmdwithstringsub);
exec->postbuf=strdup("");
} else {
if((exec->prebuf=malloc((ptr-cmdwithstringsub)+1))!=NULL) {
memcpy(exec->prebuf,cmdwithstringsub,ptr-cmdwithstringsub);
exec->prebuf[ptr-cmdwithstringsub]='\0';
}
exec->postbuf=strdup(ptr+2);
}
if(exec->prebuf==NULL || exec->postbuf==NULL) {
exec_free(exec),exec=NULL;
return(NULL); /* insuf. mem. */
}
return(exec);
}
void
exec_free(exec_t *exec)
{
if(exec==NULL)
return;
if(exec->pid!=-1)
exec_close(exec);
if(exec->name!=NULL)
free(exec->name),exec->name=NULL;
if(exec->prebuf!=NULL)
free(exec->prebuf),exec->prebuf=NULL;
if(exec->postbuf!=NULL)
free(exec->postbuf),exec->postbuf=NULL;
if(exec->fdin!=-1)
close(exec->fdin),exec->fdin=-1;
if(exec->fdout!=-1)
close(exec->fdout),exec->fdout=-1;
if(exec->fderr!=-1)
close(exec->fderr),exec->fderr=-1;
free(exec),exec=NULL;
return;
}
int
exec_open(exec_t *exec, char *stringsub)
{
char cmd[1024];
int i,n;
int pipein[2],pipeout[2],pipeerr[2];
int in_error;
if(exec==NULL)
return(-1); /* sanity check error */
if(exec->pid!=-1)
return(-1); /* there is already a running child */
snprintf(cmd,sizeof(cmd),"%s%s%s",exec->prebuf,(exec->has_param && stringsub!=NULL)?stringsub:"",exec->postbuf);
cmd[sizeof(cmd)-1]='\0';
pipein[RD]=pipein[WR]=-1;
pipeout[RD]=pipeout[WR]=-1;
pipeerr[RD]=pipeerr[WR]=-1;
in_error=0;
if(pipe(pipein)==-1 || pipe(pipeout)==-1 || pipe(pipeerr)==-1)
in_error=1;
if(in_error==0 && (exec->pid=fork())==0) {
char *params[1024];
int usedparams;
char *ptr,*end,*realend;
char endchar;
realend=cmd+strlen(cmd);
for(usedparams=0,ptr=cmd
;ptr!=realend && usedparams<((sizeof(params)/sizeof(params[0]))-1)
;
) {
endchar=(ptr[0]=='\"')?'\"':' ';
ptr+=(endchar=='\"')?1:0;
params[usedparams++]=ptr;
for(end=strchr(ptr,endchar)
;end!=NULL
;end=strchr(end+1,endchar)
) {
for(n=0;(end-(n+1))>=ptr && end[-(n+1)]=='\\';) {
n++;
}
if((n%2)==1)
continue; /* this '\"' or ' ' is escaped */
break; /* found the first unescaped '\"' or ' ' */
}
end=(end==NULL)?realend:end;
*end='\0';
ptr=(end<realend)?end+1:realend;
if(endchar=='\"' && ptr[0]==' ')
ptr++;
}
params[usedparams]=NULL;
if(usedparams==0)
exit(1); /* nothing to execute */
dup2(pipein[RD],0);
dup2(pipeout[WR],1);
dup2(pipeerr[WR],2);
for(i=3;i<1024;i++)
close(i);
execve(params[0],params,exec->envp);
exit(2); /* couldn't execve */
} else if(in_error==0 && exec->pid>0) {
close(pipein[RD]),pipein[RD]=-1;
close(pipeout[WR]),pipeout[WR]=-1;
close(pipeerr[WR]),pipeerr[WR]=-1;
exec->fdin=pipein[WR],pipein[WR]=-1;
exec->fdout=pipeout[RD],pipeout[RD]=-1;
exec->fderr=pipeerr[RD],pipeerr[RD]=-1;
} else {
in_error=1;
}
if(in_error) {
int *curfd[]={pipein,pipein+1,pipeout,pipeout+1,pipeerr,pipeerr+1};
for(i=0;i<(sizeof(curfd)/sizeof(curfd[0]));i++) {
if(*(curfd[i])!=-1)
close(*(curfd[i])),*(curfd[i])=-1;
}
return(-1); /* was in error */
}
return(0);
}
int
exec_close(exec_t *exec)
{
if(exec==NULL)
return(-1); /* sanity check failed */
if(exec->pid==-1)
return(-1); /* nothing to do as child is not started */
kill(exec->pid,SIGTERM);
return(0);
}
int
exec_reap(exec_t *exec1, /* exec_t *exec2, */ ...)
{
int status;
int flag_reaped;
exec_t *exec;
va_list ap;
flag_reaped=0;
va_start(ap, exec1);
for(exec=exec1;exec!=NULL;exec=va_arg(ap,exec_t *)) {
if(exec->pid==-1)
continue;
if(waitpid(exec->pid,&status,WNOHANG)==exec->pid) {
exec->pid=-1;
exec->laststatus=status;
close(exec->fdin),exec->fdin=-1;
close(exec->fdout),exec->fdout=-1;
close(exec->fderr),exec->fderr=-1;
flag_reaped=1;
continue;
}
}
va_end(ap);
return((flag_reaped==0)?-1:0); /* -1: no child has exited, 0: at least one child exited */
}
int
executil_installsignal(int sig, void (*f)(int))
{
struct sigaction sa;
sa.sa_handler=f;
sigemptyset(&sa.sa_mask);
sa.sa_flags=0;
return(sigaction(sig,&sa,NULL));
}
int
executil_queued(int fd)
{
int n;
if(ioctl(fd,FIONREAD,&n)!=0)
return(-1);
return(n);
}
exec_t *
executil_fd2exec(int fd, exec_t *exec1, /* exec_t *exec2, */ ...)
{
exec_t *exec;
va_list ap;
va_start(ap, exec1);
for(exec=exec1;exec!=NULL;exec=va_arg(ap,exec_t *)) {
if(exec->fdin==fd || exec->fdout==fd || exec->fderr==fd)
break;
}
va_end(ap);
return(exec);
}