From: Tulio A M Mendes <tadryanom@hotmail.com>
Date: Wed, 11 Feb 2026 22:22:37 +0000 (-0300)
Subject: feat: add minimal POSIX sh shell (/bin/sh)
X-Git-Url: https://projects.tadryanom.me/docs/POSIX_ROADMAP.md?a=commitdiff_plain;h=2e215074380829207d9955dc3eab8ca230e81803;p=AdrOS.git

feat: add minimal POSIX sh shell (/bin/sh)

- user/sh.c: minimal sh-compatible shell with:
  - Line reading from stdin
  - Argument parsing (whitespace-delimited)
  - PATH resolution (/bin/, /disk/bin/)
  - Input/output redirection (< and >)
  - Pipeline support (up to 4 stages with |)
  - Builtins: exit, echo
  - External commands via fork+execve+waitpid
- Makefile: added SH_ELF build rule and initrd packaging as /bin/sh
- cppcheck clean, 19/19 smoke tests pass
---

diff --git a/Makefile b/Makefile
index f52092a..88a8bf0 100644
--- a/Makefile
+++ b/Makefile
@@ -46,6 +46,7 @@ ifeq ($(ARCH),x86)
 
     USER_ELF := user/init.elf
     ECHO_ELF := user/echo.elf
+    SH_ELF := user/sh.elf
     INITRD_IMG := initrd.img
     MKINITRD := tools/mkinitrd
 endif
@@ -130,8 +131,11 @@ $(USER_ELF): user/init.c user/linker.ld
 $(ECHO_ELF): user/echo.c user/linker.ld
 	@i686-elf-gcc -m32 -I include -ffreestanding -fno-pie -no-pie -nostdlib -Wl,-T,user/linker.ld -o $(ECHO_ELF) user/echo.c user/errno.c
 
-$(INITRD_IMG): $(MKINITRD) $(USER_ELF) $(ECHO_ELF)
-	@./$(MKINITRD) $(INITRD_IMG) $(USER_ELF):bin/init.elf $(ECHO_ELF):bin/echo.elf
+$(SH_ELF): user/sh.c user/linker.ld
+	@i686-elf-gcc -m32 -I include -ffreestanding -fno-pie -no-pie -nostdlib -Wl,-T,user/linker.ld -o $(SH_ELF) user/sh.c user/errno.c
+
+$(INITRD_IMG): $(MKINITRD) $(USER_ELF) $(ECHO_ELF) $(SH_ELF)
+	@./$(MKINITRD) $(INITRD_IMG) $(USER_ELF):bin/init.elf $(ECHO_ELF):bin/echo.elf $(SH_ELF):bin/sh
 
 run: iso
 	@rm -f serial.log qemu.log
diff --git a/user/sh.c b/user/sh.c
new file mode 100644
index 0000000..ba5dccb
--- /dev/null
+++ b/user/sh.c
@@ -0,0 +1,329 @@
+/* AdrOS minimal POSIX sh */
+#include <stdint.h>
+#include "user_errno.h"
+
+enum {
+    SYSCALL_WRITE   = 1,
+    SYSCALL_EXIT    = 2,
+    SYSCALL_GETPID  = 3,
+    SYSCALL_OPEN    = 4,
+    SYSCALL_READ    = 5,
+    SYSCALL_CLOSE   = 6,
+    SYSCALL_WAITPID = 7,
+    SYSCALL_DUP2    = 13,
+    SYSCALL_PIPE    = 14,
+    SYSCALL_EXECVE  = 15,
+    SYSCALL_FORK    = 16,
+};
+
+enum { O_RDONLY = 0, O_WRONLY = 1, O_CREAT = 0x40, O_TRUNC = 0x200 };
+
+/* ---- syscall wrappers ---- */
+
+static int sys_write(int fd, const void* buf, uint32_t len) {
+    int ret;
+    __asm__ volatile("int $0x80" : "=a"(ret)
+        : "a"(SYSCALL_WRITE), "b"(fd), "c"(buf), "d"(len) : "memory");
+    return __syscall_fix(ret);
+}
+
+static int sys_read(int fd, void* buf, uint32_t len) {
+    int ret;
+    __asm__ volatile("int $0x80" : "=a"(ret)
+        : "a"(SYSCALL_READ), "b"(fd), "c"(buf), "d"(len) : "memory");
+    return __syscall_fix(ret);
+}
+
+static int sys_open(const char* path, int flags) {
+    int ret;
+    __asm__ volatile("int $0x80" : "=a"(ret)
+        : "a"(SYSCALL_OPEN), "b"(path), "c"(flags) : "memory");
+    return __syscall_fix(ret);
+}
+
+static int sys_close(int fd) {
+    int ret;
+    __asm__ volatile("int $0x80" : "=a"(ret)
+        : "a"(SYSCALL_CLOSE), "b"(fd) : "memory");
+    return __syscall_fix(ret);
+}
+
+static int sys_fork(void) {
+    int ret;
+    __asm__ volatile("int $0x80" : "=a"(ret)
+        : "a"(SYSCALL_FORK) : "memory");
+    return __syscall_fix(ret);
+}
+
+static int sys_execve(const char* p, char* const* av,
+                      char* const* ev) {
+    int ret;
+    __asm__ volatile("int $0x80" : "=a"(ret)
+        : "a"(SYSCALL_EXECVE), "b"(p), "c"(av), "d"(ev) : "memory");
+    return __syscall_fix(ret);
+}
+
+static int sys_waitpid(int pid, int* status, int opts) {
+    int ret;
+    __asm__ volatile("int $0x80" : "=a"(ret)
+        : "a"(SYSCALL_WAITPID), "b"(pid), "c"(status), "d"(opts) : "memory");
+    return __syscall_fix(ret);
+}
+
+static int sys_dup2(int oldfd, int newfd) {
+    int ret;
+    __asm__ volatile("int $0x80" : "=a"(ret)
+        : "a"(SYSCALL_DUP2), "b"(oldfd), "c"(newfd) : "memory");
+    return __syscall_fix(ret);
+}
+
+static int sys_pipe(int fds[2]) {
+    int ret;
+    __asm__ volatile("int $0x80" : "=a"(ret)
+        : "a"(SYSCALL_PIPE), "b"(fds) : "memory");
+    return __syscall_fix(ret);
+}
+
+static __attribute__((noreturn)) void sys_exit(int code) {
+    __asm__ volatile("int $0x80" : : "a"(SYSCALL_EXIT), "b"(code) : "memory");
+    for (;;) __asm__ volatile("hlt");
+}
+
+/* ---- string helpers ---- */
+
+static uint32_t slen(const char* s) {
+    uint32_t n = 0;
+    while (s && s[n]) n++;
+    return n;
+}
+
+static void wr(int fd, const char* s) {
+    (void)sys_write(fd, s, slen(s));
+}
+
+static int scmp(const char* a, const char* b) {
+    while (*a && *b && *a == *b) { a++; b++; }
+    return (unsigned char)*a - (unsigned char)*b;
+}
+
+static void scpy(char* d, const char* s) {
+    while (*s) *d++ = *s++;
+    *d = 0;
+}
+
+/* ---- line reading ---- */
+
+#define LINE_MAX 256
+#define MAX_ARGS 32
+
+static char line[LINE_MAX];
+
+static int read_line(void) {
+    uint32_t pos = 0;
+    while (pos < LINE_MAX - 1) {
+        char c;
+        int r = sys_read(0, &c, 1);
+        if (r <= 0) {
+            if (pos == 0) return -1;
+            break;
+        }
+        if (c == '\n' || c == '\r') break;
+        if ((c == '\b' || c == 127) && pos > 0) { pos--; continue; }
+        if (c >= ' ' && c <= '~') line[pos++] = c;
+    }
+    line[pos] = 0;
+    return (int)pos;
+}
+
+/* ---- argument parsing ---- */
+
+static int parse_args(char* cmd, char** argv, int max) {
+    int argc = 0;
+    char* p = cmd;
+    while (*p && argc < max - 1) {
+        while (*p == ' ' || *p == '\t') p++;
+        if (*p == 0) break;
+        argv[argc++] = p;
+        while (*p && *p != ' ' && *p != '\t') p++;
+        if (*p) *p++ = 0;
+    }
+    argv[argc] = 0;
+    return argc;
+}
+
+/* ---- PATH resolution ---- */
+
+static char pathbuf[256];
+
+static const char* resolve(const char* cmd) {
+    if (cmd[0] == '/' || cmd[0] == '.') return cmd;
+    static const char* dirs[] = { "/bin/", "/disk/bin/", 0 };
+    for (int i = 0; dirs[i]; i++) {
+        scpy(pathbuf, dirs[i]);
+        scpy(pathbuf + slen(pathbuf), cmd);
+        int fd = sys_open(pathbuf, O_RDONLY);
+        if (fd >= 0) { sys_close(fd); return pathbuf; }
+    }
+    return cmd;
+}
+
+/* ---- run a single simple command ---- */
+
+static void run_simple(char* cmd) {
+    char* argv[MAX_ARGS];
+    int argc = parse_args(cmd, argv, MAX_ARGS);
+    if (argc == 0) return;
+
+    /* extract redirections */
+    char* redir_out = 0;
+    char* redir_in  = 0;
+    int nargc = 0;
+    for (int i = 0; i < argc; i++) {
+        if (scmp(argv[i], ">") == 0 && i + 1 < argc) {
+            redir_out = argv[++i];
+        } else if (scmp(argv[i], "<") == 0 && i + 1 < argc) {
+            redir_in = argv[++i];
+        } else {
+            argv[nargc++] = argv[i];
+        }
+    }
+    argv[nargc] = 0;
+    argc = nargc;
+    if (argc == 0) return;
+
+    /* builtin: exit */
+    if (scmp(argv[0], "exit") == 0) {
+        int code = 0;
+        if (argc > 1) {
+            const char* s = argv[1];
+            while (*s >= '0' && *s <= '9') {
+                code = code * 10 + (*s - '0');
+                s++;
+            }
+        }
+        sys_exit(code);
+    }
+
+    /* builtin: echo */
+    if (scmp(argv[0], "echo") == 0) {
+        for (int i = 1; i < argc; i++) {
+            if (i > 1) wr(1, " ");
+            wr(1, argv[i]);
+        }
+        wr(1, "\n");
+        return;
+    }
+
+    /* external command */
+    const char* path = resolve(argv[0]);
+    int pid = sys_fork();
+    if (pid < 0) { wr(2, "sh: fork failed\n"); return; }
+
+    if (pid == 0) {
+        /* child */
+        if (redir_in) {
+            int fd = sys_open(redir_in, O_RDONLY);
+            if (fd >= 0) { sys_dup2(fd, 0); sys_close(fd); }
+        }
+        if (redir_out) {
+            int fd = sys_open(redir_out, O_WRONLY | O_CREAT | O_TRUNC);
+            if (fd >= 0) { sys_dup2(fd, 1); sys_close(fd); }
+        }
+        sys_execve(path, argv, 0);
+        wr(2, "sh: ");
+        wr(2, argv[0]);
+        wr(2, ": not found\n");
+        sys_exit(127);
+    }
+
+    /* parent waits */
+    int st;
+    sys_waitpid(pid, &st, 0);
+}
+
+/* ---- pipeline support ---- */
+
+static void run_pipeline(char* cmdline) {
+    /* split on '|' */
+    char* cmds[4];
+    int ncmds = 0;
+    cmds[0] = cmdline;
+    for (char* p = cmdline; *p; p++) {
+        if (*p == '|' && ncmds < 3) {
+            *p = 0;
+            cmds[++ncmds] = p + 1;
+        }
+    }
+    ncmds++;
+
+    if (ncmds == 1) {
+        run_simple(cmds[0]);
+        return;
+    }
+
+    /* multi-stage pipeline */
+    int prev_rd = -1;
+    for (int i = 0; i < ncmds; i++) {
+        int pfd[2] = {-1, -1};
+        if (i < ncmds - 1) {
+            if (sys_pipe(pfd) < 0) {
+                wr(2, "sh: pipe failed\n");
+                return;
+            }
+        }
+
+        int pid = sys_fork();
+        if (pid < 0) { wr(2, "sh: fork failed\n"); return; }
+
+        if (pid == 0) {
+            if (prev_rd >= 0) { sys_dup2(prev_rd, 0); sys_close(prev_rd); }
+            if (pfd[1] >= 0)  { sys_dup2(pfd[1], 1); sys_close(pfd[1]); }
+            if (pfd[0] >= 0)  sys_close(pfd[0]);
+
+            char* argv[MAX_ARGS];
+            int argc = parse_args(cmds[i], argv, MAX_ARGS);
+            if (argc == 0) sys_exit(0);
+            const char* path = resolve(argv[0]);
+            sys_execve(path, argv, 0);
+            wr(2, "sh: ");
+            wr(2, argv[0]);
+            wr(2, ": not found\n");
+            sys_exit(127);
+        }
+
+        /* parent */
+        if (prev_rd >= 0) sys_close(prev_rd);
+        if (pfd[1] >= 0)  sys_close(pfd[1]);
+        prev_rd = pfd[0];
+    }
+
+    if (prev_rd >= 0) sys_close(prev_rd);
+
+    /* wait for all children */
+    for (int i = 0; i < ncmds; i++) {
+        int st;
+        sys_waitpid(-1, &st, 0);
+    }
+}
+
+/* ---- main loop ---- */
+
+static void sh_main(void) {
+    wr(1, "$ ");
+    while (1) {
+        int len = read_line();
+        if (len < 0) break;
+        if (len > 0) run_pipeline(line);
+        wr(1, "$ ");
+    }
+}
+
+__attribute__((naked)) void _start(void) {
+    __asm__ volatile(
+        "call sh_main\n"
+        "mov $0, %ebx\n"
+        "mov $2, %eax\n"
+        "int $0x80\n"
+        "hlt\n"
+    );
+}