ls.c

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/*      ls 5.4 - List files.                            Author: Kees J. Bot
 *                                                              25 Apr 1989
 *
 * About the amount of bytes for heap + stack under Minix:
 * Ls needs a average amount of 42 bytes per unserviced directory entry, so
 * scanning 10 directory levels deep in an ls -R with 100 entries per directory
 * takes 42000 bytes of heap.  So giving ls 10000 bytes is tight, 20000 is
 * usually enough, 40000 is pessimistic.
 */

/* The array l_ifmt[] is used in an 'ls -l' to map the type of a file to a
 * letter.  This is done so that ls can list any future file or device type
 * other than symlinks, without recompilation.  (Yes it's dirty.)
 */
char l_ifmt[] = "0pcCd?bB-?l?s???";

#define ifmt(mode)      l_ifmt[((mode) >> 12) & 0xF]

#define nil 0
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <dirent.h>
#include <time.h>
#include <pwd.h>
#include <grp.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <termios.h>
#include <sys/ioctl.h>

#ifndef major
#define major(dev)      ((int) (((dev) >> 8) & 0xFF))
#define minor(dev)      ((int) (((dev) >> 0) & 0xFF))
#endif

#if !__minix
#define SUPER_ID        uid     /* Let -A flag be default for SUPER_ID == 0. */
#else
#define SUPER_ID        gid
#endif

#ifdef S_IFLNK
int (*status)(const char *file, struct stat *stp);
#else
#define status  stat
#endif

/* Basic disk block size is 512 except for one niche O.S. */
#if __minix
#define BLOCK   1024
#else
#define BLOCK    512
#endif

/* Assume other systems have st_blocks. */
#if !__minix
#define ST_BLOCKS 1
#endif

/* Some terminals ignore more than 80 characters on a line.  Dumb ones wrap
 * when the cursor hits the side.  Nice terminals don't wrap until they have
 * to print the 81st character.  Whether we like it or not, no column 80.
 */
int ncols= 79;

#define NSEP    3       /* # spaces between columns. */

#define MAXCOLS 128     /* Max # of files per line. */

char *arg0;     /* Last component of argv[0]. */
int uid, gid;   /* callers id. */
int ex= 0;      /* Exit status to be. */
int istty;      /* Output is on a terminal. */

/* Safer versions of malloc and realloc: */

void heaperr(void)
{
        fprintf(stderr, "%s: Out of memory\n", arg0);
        exit(-1);
}

void *allocate(size_t n)
/* Deliver or die. */
{
        void *a;

        if ((a= malloc(n)) == nil) heaperr();
        return a;
}

void *reallocate(void *a, size_t n)
{
        if ((a= realloc(a, n)) == nil) heaperr();
        return a;
}

char allowed[] = "acdfghilnpqrstu1ACDFLMRTX";
char flags[sizeof(allowed)];

char arg0flag[] = "cdfmrtx";    /* These in argv[0] go to upper case. */

void setflags(char *flgs)
{
        int c;

        while ((c= *flgs++) != 0) {
                if (strchr(allowed, c) == nil) {
                        fprintf(stderr, "Usage: %s [-%s] [file ...]\n",
                                arg0, allowed);
                        exit(1);
                } else
                if (strchr(flags, c) == nil) {
                        flags[strlen(flags)] = c;
                }
        }
}

int present(int f)
{
        return f == 0 || strchr(flags, f) != nil;
}

void report(char *f)
/* Like perror(3), but in the style: "ls: junk: No such file or directory. */
{
        fprintf(stderr, "%s: %s: %s\n", arg0, f, strerror(errno));
        ex= 1;
}

/* Two functions, uidname and gidname, translate id's to readable names.
 * All names are remembered to avoid searching the password file.
 */
#define NNAMES  (1 << (sizeof(int) + sizeof(char *)))
enum whatmap { PASSWD, GROUP };

struct idname {         /* Hash list of names. */
        struct idname   *next;
        char            *name;
        uid_t           id;
} *uids[NNAMES], *gids[NNAMES];

char *idname(unsigned id, enum whatmap map)
/* Return name for a given user/group id. */
{
        struct idname *i;
        struct idname **ids= &(map == PASSWD ? uids : gids)[id % NNAMES];

        while ((i= *ids) != nil && id < i->id) ids= &i->next;

        if (i == nil || id != i->id) {
                /* Not found, go look in the password or group map. */
                char *name= nil;
                char noname[3 * sizeof(uid_t)];

                if (!present('n')) {
                        if (map == PASSWD) {
                                struct passwd *pw= getpwuid(id);

                                if (pw != nil) name= pw->pw_name;
                        } else {
                                struct group *gr= getgrgid(id);

                                if (gr != nil) name= gr->gr_name;
                        }
                }
                if (name == nil) {
                        /* Can't find it, weird.  Use numerical "name." */
                        sprintf(noname, "%u", id);
                        name= noname;
                }

                /* Add a new id-to-name cell. */
                i= allocate(sizeof(*i));
                i->id= id;
                i->name= allocate(strlen(name) + 1);
                strcpy(i->name, name);
                i->next= *ids;
                *ids= i;
        }
        return i->name;
}

#define uidname(uid)    idname((uid), PASSWD)
#define gidname(gid)    idname((gid), GROUP)

/* Path name construction, addpath adds a component, delpath removes it.
 * The string path is used throughout the program as the file under examination.
 */

char *path;     /* Path name constructed in path[]. */
int plen= 0, pidx= 0;   /* Lenght/index for path[]. */

void addpath(int *didx, char *name)
/* Add a component to path. (name may also be a full path at the first call)
 * The index where the current path ends is stored in *pdi.
 */
{
        if (plen == 0) path= (char *) allocate((plen= 32) * sizeof(path[0]));

        if (pidx == 1 && path[0] == '.') pidx= 0;       /* Remove "." */

        *didx= pidx;    /* Record point to go back to for delpath. */

        if (pidx > 0 && path[pidx-1] != '/') path[pidx++]= '/';

        do {
                if (*name != '/' || pidx == 0 || path[pidx-1] != '/') {
                        if (pidx == plen) {
                                path= (char *) reallocate((void *) path,
                                                (plen*= 2) * sizeof(path[0]));
                        }
                        path[pidx++]= *name;
                }
        } while (*name++ != 0);

        --pidx;         /* Put pidx back at the null.  The path[pidx++]= '/'
                         * statement will overwrite it at the next call.
                         */
}

#define delpath(didx)   (path[pidx= didx]= 0)   /* Remove component. */

int field = 0;  /* (used to be) Fields that must be printed. */
                /* (now) Effects triggered by certain flags. */

#define L_INODE         0x0001  /* -i */
#define L_BLOCKS        0x0002  /* -s */
#define L_EXTRA         0x0004  /* -X */
#define L_MODE          0x0008  /* -lMX */
#define L_LONG          0x0010  /* -l */
#define L_GROUP         0x0020  /* -g */
#define L_BYTIME        0x0040  /* -tuc */
#define L_ATIME         0x0080  /* -u */
#define L_CTIME         0x0100  /* -c */
#define L_MARK          0x0200  /* -F */
#define L_MARKDIR       0x0400  /* -p */
#define L_TYPE          0x0800  /* -D */
#define L_LONGTIME      0x1000  /* -T */
#define L_DIR           0x2000  /* -d */
#define L_KMG           0x4000  /* -h */

struct file {           /* A file plus stat(2) information. */
        struct file     *next;  /* Lists are made of them. */
        char            *name;  /* Null terminated name. */
        ino_t           ino;
        mode_t          mode;
        uid_t           uid;
        gid_t           gid;
        nlink_t         nlink;
        dev_t           rdev;
        off_t           size;
        time_t          mtime;
        time_t          atime;
        time_t          ctime;
#if ST_BLOCKS
        long            blocks;
#endif
};

void setstat(struct file *f, struct stat *stp)
{
        f->ino=         stp->st_ino;
        f->mode=        stp->st_mode;
        f->nlink=       stp->st_nlink;
        f->uid=         stp->st_uid;
        f->gid=         stp->st_gid;
        f->rdev=        stp->st_rdev;
        f->size=        stp->st_size;
        f->mtime=       stp->st_mtime;
        f->atime=       stp->st_atime;
        f->ctime=       stp->st_ctime;
#if ST_BLOCKS
        f->blocks=      stp->st_blocks;
#endif
}

#define PAST    (26*7*24*3600L) /* Half a year ago. */
/* Between PAST and FUTURE from now a time is printed, otherwise a year. */
#define FUTURE  ( 1*7*24*3600L) /* One week. */

static char *timestamp(struct file *f)
/* Transform the right time field into something readable. */
{
        struct tm *tm;
        time_t t;
        static time_t now;
        static int drift= 0;
        static char date[] = "Jan 19 03:14:07 2038";
        static char month[] = "JanFebMarAprMayJunJulAugSepOctNovDec";

        t= f->mtime;
        if (field & L_ATIME) t= f->atime;
        if (field & L_CTIME) t= f->ctime;

        tm= localtime(&t);
        if (--drift < 0) { time(&now); drift= 50; }     /* limit time() calls */

        if (field & L_LONGTIME) {
                sprintf(date, "%.3s %2d %02d:%02d:%02d %d",
                        month + 3*tm->tm_mon,
                        tm->tm_mday,
                        tm->tm_hour, tm->tm_min, tm->tm_sec,
                        1900 + tm->tm_year);
        } else
        if (t < now - PAST || t > now + FUTURE) {
                sprintf(date, "%.3s %2d  %d",
                        month + 3*tm->tm_mon,
                        tm->tm_mday,
                        1900 + tm->tm_year);
        } else {
                sprintf(date, "%.3s %2d %02d:%02d",
                        month + 3*tm->tm_mon,
                        tm->tm_mday,
                        tm->tm_hour, tm->tm_min);
        }
        return date;
}

char *permissions(struct file *f)
/* Compute long or short rwx bits. */
{
        static char rwx[] = "drwxr-x--x";

        rwx[0] = ifmt(f->mode);
        /* Note that rwx[0] is a guess for the more alien file types.  It is
         * correct for BSD4.3 and derived systems.  I just don't know how
         * "standardized" these numbers are.
         */

        if (field & L_EXTRA) {          /* Short style */
                int mode = f->mode, ucase= 0;

                if (uid == f->uid) {    /* What group of bits to use. */
                        /* mode<<= 0, */
                        ucase= (mode<<3) | (mode<<6);
                        /* Remember if group or others have permissions. */
                } else
                if (gid == f->gid) {
                        mode<<= 3;
                } else {
                        mode<<= 6;
                }
                rwx[1]= mode&S_IRUSR ? (ucase&S_IRUSR ? 'R' : 'r') : '-';
                rwx[2]= mode&S_IWUSR ? (ucase&S_IWUSR ? 'W' : 'w') : '-';

                if (mode&S_IXUSR) {
                        static char sbit[]= { 'x', 'g', 'u', 's' };

                        rwx[3]= sbit[(f->mode&(S_ISUID|S_ISGID))>>10];
                        if (ucase&S_IXUSR) rwx[3] += 'A'-'a';
                } else {
                        rwx[3]= f->mode&(S_ISUID|S_ISGID) ? '=' : '-';
                }
                rwx[4]= 0;
        } else {                /* Long form. */
                char *p= rwx+1;
                int mode= f->mode;

                do {
                        p[0] = (mode & S_IRUSR) ? 'r' : '-';
                        p[1] = (mode & S_IWUSR) ? 'w' : '-';
                        p[2] = (mode & S_IXUSR) ? 'x' : '-';
                        mode<<= 3;
                } while ((p+=3) <= rwx+7);

                if (f->mode&S_ISUID) rwx[3]= f->mode&(S_IXUSR>>0) ? 's' : '=';
                if (f->mode&S_ISGID) rwx[6]= f->mode&(S_IXUSR>>3) ? 's' : '=';
                if (f->mode&S_ISVTX) rwx[9]= f->mode&(S_IXUSR>>6) ? 't' : '=';
        }
        return rwx;
}

void numeral(int i, char **pp)
{
        char itoa[3*sizeof(int)], *a=itoa;

        do *a++ = i%10 + '0'; while ((i/=10) > 0);

        do *(*pp)++ = *--a; while (a>itoa);
}

#define K       1024L           /* A kilobyte counts in multiples of K */
#define T       1000L           /* A megabyte in T*K, a gigabyte in T*T*K */

char *cxsize(struct file *f)
/* Try and fail to turn a 32 bit size into 4 readable characters. */
{
        static char siz[] = "1.2m";
        char *p= siz;
        off_t z;

        siz[1]= siz[2]= siz[3]= 0;

        if (f->size <= 5*K) {   /* <= 5K prints as is. */
                numeral((int) f->size, &p);
                return siz;
        }
        z= (f->size + K-1) / K;

        if (z <= 999) {         /* Print as 123k. */
                numeral((int) z, &p);
                *p = 'k';       /* Can't use 'K', looks bad */
        } else
        if (z*10 <= 99*T) {     /* 1.2m (Try ls -X /dev/at0) */
                z= (z*10 + T-1) / T;    /* Force roundup */
                numeral((int) z / 10, &p);
                *p++ = '.';
                numeral((int) z % 10, &p);
                *p = 'm';
        } else
        if (z <= 999*T) {       /* 123m */
                numeral((int) ((z + T-1) / T), &p);
                *p = 'm';
        } else {                /* 1.2g */
                z= (z*10 + T*T-1) / (T*T);
                numeral((int) z / 10, &p);
                *p++ = '.';
                numeral((int) z % 10, &p);
                *p = 'g';
        }
        return siz;
}

/* Transform size of file to number of blocks.  This was once a function that
 * guessed the number of indirect blocks, but that nonsense has been removed.
 */
#if ST_BLOCKS
#define nblocks(f)      ((f)->blocks)
#else
#define nblocks(f)      (((f)->size + BLOCK-1) / BLOCK)
#endif

/* From number of blocks to kilobytes. */
#if BLOCK < 1024
#define nblk2k(nb)      (((nb) + (1024 / BLOCK - 1)) / (1024 / BLOCK))
#else
#define nblk2k(nb)      ((nb) * (BLOCK / 1024))
#endif

static int (*CMP)(struct file *f1, struct file *f2);
static int (*rCMP)(struct file *f1, struct file *f2);

static void mergesort(struct file **al)
/* This is either a stable mergesort, or thermal noise, I'm no longer sure.
 * It must be called like this: if (L != nil && L->next != nil) mergesort(&L);
 */
{
        /* static */ struct file *l1, **mid;  /* Need not be local */
        struct file *l2;

        l1= *(mid= &(*al)->next);
        do {
                if ((l1= l1->next) == nil) break;
                mid= &(*mid)->next;
        } while ((l1= l1->next) != nil);

        l2= *mid;
        *mid= nil;

        if ((*al)->next != nil) mergesort(al);
        if (l2->next != nil) mergesort(&l2);

        l1= *al;
        for (;;) {
                if ((*CMP)(l1, l2) <= 0) {
                        if ((l1= *(al= &l1->next)) == nil) {
                                *al= l2;
                                break;
                        }
                } else {
                        *al= l2;
                        l2= *(al= &l2->next);
                        *al= l1;
                        if (l2 == nil) break;
                }
        }
}

int namecmp(struct file *f1, struct file *f2)
{
        return strcmp(f1->name, f2->name);
}

int mtimecmp(struct file *f1, struct file *f2)
{
        return f1->mtime == f2->mtime ? 0 : f1->mtime > f2->mtime ? -1 : 1;
}

int atimecmp(struct file *f1, struct file *f2)
{
        return f1->atime == f2->atime ? 0 : f1->atime > f2->atime ? -1 : 1;
}

int ctimecmp(struct file *f1, struct file *f2)
{
        return f1->ctime == f2->ctime ? 0 : f1->ctime > f2->ctime ? -1 : 1;
}

int typecmp(struct file *f1, struct file *f2)
{
        return ifmt(f1->mode) - ifmt(f2->mode);
}

int revcmp(struct file *f1, struct file *f2) { return (*rCMP)(f2, f1); }

static void sort(struct file **al)
/* Sort the files according to the flags. */
{
        if (!present('f') && *al != nil && (*al)->next != nil) {
                CMP= namecmp;

                if (!(field & L_BYTIME)) {
                        /* Sort on name */

                        if (present('r')) { rCMP= CMP; CMP= revcmp; }
                        mergesort(al);
                } else {
                        /* Sort on name first, then sort on time. */

                        mergesort(al);
                        if (field & L_CTIME) {
                                CMP= ctimecmp;
                        } else
                        if (field & L_ATIME) {
                                CMP= atimecmp;
                        } else {
                                CMP= mtimecmp;
                        }

                        if (present('r')) { rCMP= CMP; CMP= revcmp; }
                        mergesort(al);
                }
                /* Separate by file type if so desired. */

                if (field & L_TYPE) {
                        CMP= typecmp;
                        mergesort(al);
                }
        }
}

struct file *newfile(char *name)
/* Create file structure for given name. */
{
        struct file *new;

        new= (struct file *) allocate(sizeof(*new));
        new->name= strcpy((char *) allocate(strlen(name)+1), name);
        return new;
}

void pushfile(struct file **flist, struct file *new)
/* Add file to the head of a list. */
{
        new->next= *flist;
        *flist= new;
}

void delfile(struct file *old)
/* Release old file structure. */
{
        free((void *) old->name);
        free((void *) old);
}

struct file *popfile(struct file **flist)
/* Pop file off top of file list. */
{
        struct file *f;

        f= *flist;
        *flist= f->next;
        return f;
}

int dotflag(char *name)
/* Return flag that would make ls list this name: -a or -A. */
{
        if (*name++ != '.') return 0;

        switch (*name++) {
        case 0:         return 'a';                     /* "." */
        case '.':       if (*name == 0) return 'a';     /* ".." */
        default:        return 'A';                     /* ".*" */
        }
}

int adddir(struct file **aflist, char *name)
/* Add directory entries of directory name to a file list. */
{
        DIR *d;
        struct dirent *e;

        if (access(name, 0) < 0) {
                report(name);
                return 0;
        }

        if ((d= opendir(name)) == nil) {
                report(name);
                return 0;
        }
        while ((e= readdir(d)) != nil) {
                if (e->d_ino != 0 && present(dotflag(e->d_name))) {
                        pushfile(aflist, newfile(e->d_name));
                        aflist= &(*aflist)->next;
                }
        }
        closedir(d);
        return 1;
}

off_t countblocks(struct file *flist)
/* Compute total block count for a list of files. */
{
        off_t cb = 0;

        while (flist != nil) {
                switch (flist->mode & S_IFMT) {
                case S_IFDIR:
                case S_IFREG:
#ifdef S_IFLNK
                case S_IFLNK:
#endif
                        cb += nblocks(flist);
                }
                flist= flist->next;
        }
        return cb;
}

void printname(char *name)
/* Print a name with control characters as '?' (unless -q).  The terminal is
 * assumed to be eight bit clean.
 */
{
        int c, q= present('q');

        while ((c= (unsigned char) *name++) != 0) {
                if (q && (c < ' ' || c == 0177)) c= '?';
                putchar(c);
        }
}

int mark(struct file *f, int doit)
{
        int c;

        c= 0;

        if (field & L_MARK) {
                switch (f->mode & S_IFMT) {
                case S_IFDIR:   c= '/'; break;
#ifdef S_IFIFO
                case S_IFIFO:   c= '|'; break;
#endif
#ifdef S_IFLNK
                case S_IFLNK:   c= '@'; break;
#endif
#ifdef S_IFSOCK
                case S_IFSOCK:  c= '='; break;
#endif
                case S_IFREG:
                        if (f->mode & (S_IXUSR | S_IXGRP | S_IXOTH)) c= '*';
                        break;
                }
        } else
        if (field & L_MARKDIR) {
                if (S_ISDIR(f->mode)) c= '/';
        }

        if (doit && c != 0) putchar(c);
        return c;
}

/* Width of entire column, and of several fields. */
enum { W_COL, W_INO, W_BLK, W_NLINK, W_UID, W_GID, W_SIZE, W_NAME, MAXFLDS };

unsigned char fieldwidth[MAXCOLS][MAXFLDS];

void maxise(unsigned char *aw, int w)
/* Set *aw to the larger of it and w. */
{
        if (w > *aw) {
                if (w > UCHAR_MAX) w= UCHAR_MAX;
                *aw= w;
        }
}

int numwidth(unsigned long n)
/* Compute width of 'n' when printed. */
{
        int width= 0;

        do { width++; } while ((n /= 10) > 0);
        return width;
}

#if !__minix
int numxwidth(unsigned long n)
/* Compute width of 'n' when printed in hex. */
{
        int width= 0;

        do { width++; } while ((n /= 16) > 0);
        return width;
}
#endif

static int nsp= 0;      /* This many spaces have not been printed yet. */
#define spaces(n)       (nsp= (n))
#define terpri()        (nsp= 0, putchar('\n'))         /* No trailing spaces */

void print1(struct file *f, int col, int doit)
/* Either compute the number of spaces needed to print file f (doit == 0) or
 * really print it (doit == 1).
 */
{
        int width= 0, n;
        char *p;
        unsigned char *f1width = fieldwidth[col];

        while (nsp>0) { putchar(' '); nsp--; }/* Fill gap between two columns */

        if (field & L_INODE) {
                if (doit) {
                        printf("%*d ", f1width[W_INO], f->ino);
                } else {
                        maxise(&f1width[W_INO], numwidth(f->ino));
                        width++;
                }
        }
        if (field & L_BLOCKS) {
                unsigned long nb= nblk2k(nblocks(f));
                if (doit) {
                        printf("%*lu ", f1width[W_BLK], nb);
                } else {
                        maxise(&f1width[W_BLK], numwidth(nb));
                        width++;
                }
        }
        if (field & L_MODE) {
                if (doit) {
                        printf("%s ", permissions(f));
                } else {
                        width+= (field & L_EXTRA) ? 5 : 11;
                }
        }
        if (field & L_EXTRA) {
                p= cxsize(f);
                n= strlen(p)+1;

                if (doit) {
                        n= f1width[W_SIZE] - n;
                        while (n > 0) { putchar(' '); --n; }
                        printf("%s ", p);
                } else {
                        maxise(&f1width[W_SIZE], n);
                }
        }
        if (field & L_LONG) {
                if (doit) {
                        printf("%*u ", f1width[W_NLINK], (unsigned) f->nlink);
                } else {
                        maxise(&f1width[W_NLINK], numwidth(f->nlink));
                        width++;
                }
                if (!(field & L_GROUP)) {
                        if (doit) {
                                printf("%-*s  ", f1width[W_UID],
                                                        uidname(f->uid));
                        } else {
                                maxise(&f1width[W_UID],
                                                strlen(uidname(f->uid)));
                                width+= 2;
                        }
                }
                if (doit) {
                        printf("%-*s  ", f1width[W_GID], gidname(f->gid));
                } else {
                        maxise(&f1width[W_GID], strlen(gidname(f->gid)));
                        width+= 2;
                }

                switch (f->mode & S_IFMT) {
                case S_IFBLK:
                case S_IFCHR:
#ifdef S_IFMPB
                case S_IFMPB:
#endif
#ifdef S_IFMPC
                case S_IFMPC:
#endif
#if __minix
                        if (doit) {
                                printf("%*d, %3d ", f1width[W_SIZE] - 5,
                                        major(f->rdev), minor(f->rdev));
                        } else {
                                maxise(&f1width[W_SIZE],
                                                numwidth(major(f->rdev)) + 5);
                                width++;
                        }
#else /* !__minix */
                        if (doit) {
                                printf("%*lX ", f1width[W_SIZE],
                                        (unsigned long) f->rdev);
                        } else {
                                maxise(&f1width[W_SIZE], numwidth(f->rdev));
                                width++;
                        }
#endif /* !__minix */
                        break;
                default:
                        if (field & L_KMG) {
                                p= cxsize(f);
                                n= strlen(p)+1;

                                if (doit) {
                                        n= f1width[W_SIZE] - n;
                                        while (n > 0) { putchar(' '); --n; }
                                        printf("%s ", p);
                                } else {
                                        maxise(&f1width[W_SIZE], n);
                                }
                        } else {
                                if (doit) {
                                        printf("%*lu ", f1width[W_SIZE],
                                                (unsigned long) f->size);
                                } else {
                                        maxise(&f1width[W_SIZE],
                                                numwidth(f->size));
                                        width++;
                                }
                        }
                }

                if (doit) {
                        printf("%s ", timestamp(f));
                } else {
                        width+= (field & L_LONGTIME) ? 21 : 13;
                }
        }

        n= strlen(f->name);
        if (doit) {
                printname(f->name);
                if (mark(f, 1) != 0) n++;
#ifdef S_IFLNK
                if ((field & L_LONG) && (f->mode & S_IFMT) == S_IFLNK) {
                        char *buf;
                        int r, didx;

                        buf= (char *) allocate(((size_t) f->size + 1)
                                                        * sizeof(buf[0]));
                        addpath(&didx, f->name);
                        r= readlink(path, buf, (int) f->size);
                        delpath(didx);
                        if (r > 0) buf[r] = 0; else r=1, strcpy(buf, "?");
                        printf(" -> ");
                        printname(buf);
                        free((void *) buf);
                        n+= 4 + r;
                }
#endif
                spaces(f1width[W_NAME] - n);
        } else {
                if (mark(f, 0) != 0) n++;
#ifdef S_IFLNK
                if ((field & L_LONG) && (f->mode & S_IFMT) == S_IFLNK) {
                        n+= 4 + (int) f->size;
                }
#endif
                maxise(&f1width[W_NAME], n + NSEP);

                for (n= 1; n < MAXFLDS; n++) width+= f1width[n];
                maxise(&f1width[W_COL], width);
        }
}

int countfiles(struct file *flist)
/* Return number of files in the list. */
{
        int n= 0;

        while (flist != nil) { n++; flist= flist->next; }

        return n;
}

struct file *filecol[MAXCOLS];  /* filecol[i] is list of files for column i. */
int nfiles, nlines;     /* # files to print, # of lines needed. */

void columnise(struct file *flist, int nplin)
/* Chop list of files up in columns.  Note that 3 columns are used for 5 files
 * even though nplin may be 4, filecol[3] will simply be nil.
 */
{
        int i, j;

        nlines= (nfiles + nplin - 1) / nplin;   /* nlines needed for nfiles */

        filecol[0]= flist;

        for (i=1; i<nplin; i++) {       /* Give nlines files to each column. */
                for (j=0; j<nlines && flist != nil; j++) flist= flist->next;

                filecol[i]= flist;
        }
}

int print(struct file *flist, int nplin, int doit)
/* Try (doit == 0), or really print the list of files over nplin columns.
 * Return true if it can be done in nplin columns or if nplin == 1.
 */
{
        register struct file *f;
        register int col, fld, totlen;

        columnise(flist, nplin);

        if (!doit) {
                for (col= 0; col < nplin; col++) {
                        for (fld= 0; fld < MAXFLDS; fld++) {
                                fieldwidth[col][fld]= 0;
                        }
                }
        }

        while (--nlines >= 0) {
                totlen= 0;

                for (col= 0; col < nplin; col++) {
                        if ((f= filecol[col]) != nil) {
                                filecol[col]= f->next;
                                print1(f, col, doit);
                        }
                        if (!doit && nplin > 1) {
                                /* See if this line is not too long. */
                                if (fieldwidth[col][W_COL] == UCHAR_MAX) {
                                        return 0;
                                }
                                totlen+= fieldwidth[col][W_COL];
                                if (totlen > ncols+NSEP) return 0;
                        }
                }
                if (doit) terpri();
        }
        return 1;
}

enum depth { SURFACE, SURFACE1, SUBMERGED };
enum state { BOTTOM, SINKING, FLOATING };

void listfiles(struct file *flist, enum depth depth, enum state state)
/* Main workhorse of ls, it sorts and prints the list of files.  Flags:
 * depth: working with the command line / just one file / listing dir.
 * state: How "recursive" do we have to be.
 */
{
        struct file *dlist= nil, **afl= &flist, **adl= &dlist;
        int nplin;
        static int white = 1;   /* Nothing printed yet. */

        /* Flush everything previously printed, so new error output will
         * not intermix with files listed earlier.
         */
        fflush(stdout);

        if (field != 0 || state != BOTTOM) {    /* Need stat(2) info. */
                while (*afl != nil) {
                        static struct stat st;
                        int r, didx;

                        addpath(&didx, (*afl)->name);

                        if ((r= status(path, &st)) < 0
#ifdef S_IFLNK
                                && (status == lstat || lstat(path, &st) < 0)
#endif
                        ) {
                                if (depth != SUBMERGED || errno != ENOENT)
                                        report((*afl)->name);
                                delfile(popfile(afl));
                        } else {
                                setstat(*afl, &st);
                                afl= &(*afl)->next;
                        }
                        delpath(didx);
                }
        }
        sort(&flist);

        if (depth == SUBMERGED && (field & (L_BLOCKS | L_LONG))) {
                printf("total %ld\n", nblk2k(countblocks(flist)));
        }

        if (state == SINKING || depth == SURFACE1) {
        /* Don't list directories themselves, list their contents later. */
                afl= &flist;
                while (*afl != nil) {
                        if (((*afl)->mode & S_IFMT) == S_IFDIR) {
                                pushfile(adl, popfile(afl));
                                adl= &(*adl)->next;
                        } else {
                                afl= &(*afl)->next;
                        }
                }
        }

        if ((nfiles= countfiles(flist)) > 0) {
                /* Print files in how many columns? */
                nplin= !present('C') ? 1 : nfiles < MAXCOLS ? nfiles : MAXCOLS;

                while (!print(flist, nplin, 0)) nplin--;        /* Try first */

                print(flist, nplin, 1);         /* Then do it! */
                white = 0;
        }

        while (flist != nil) {  /* Destroy file list */
                if (state == FLOATING && (flist->mode & S_IFMT) == S_IFDIR) {
                        /* But keep these directories for ls -R. */
                        pushfile(adl, popfile(&flist));
                        adl= &(*adl)->next;
                } else {
                        delfile(popfile(&flist));
                }
        }

        while (dlist != nil) {  /* List directories */
                if (dotflag(dlist->name) != 'a' || depth != SUBMERGED) {
                        int didx;

                        addpath(&didx, dlist->name);

                        flist= nil;
                        if (adddir(&flist, path)) {
                                if (depth != SURFACE1) {
                                        if (!white) putchar('\n');
                                        printf("%s:\n", path);
                                        white = 0;
                                }
                                listfiles(flist, SUBMERGED,
                                        state == FLOATING ? FLOATING : BOTTOM);
                        }
                        delpath(didx);
                }
                delfile(popfile(&dlist));
        }
}

int main(int argc, char **argv)
{
        struct file *flist= nil, **aflist= &flist;
        enum depth depth;
        char *lsflags;
        struct winsize ws;

        uid= geteuid();
        gid= getegid();

        if ((arg0= strrchr(argv[0], '/')) == nil) arg0= argv[0]; else arg0++;
        argv++;

        if (strcmp(arg0, "ls") != 0) {
                char *p= arg0+1;

                while (*p != 0) {
                        if (strchr(arg0flag, *p) != nil) *p += 'A' - 'a';
                        p++;
                }
                setflags(arg0+1);
        }
        while (*argv != nil && (*argv)[0] == '-') {
                if ((*argv)[1] == '-' && (*argv)[2] == 0) {
                        argv++;
                        break;
                }
                setflags(*argv++ + 1);
        }

        istty= isatty(1);

        if (istty && (lsflags= getenv("LSOPTS")) != nil) {
                if (*lsflags == '-') lsflags++;
                setflags(lsflags);
        }

        if (!present('1') && !present('C') && !present('l')
                && (istty || present('M') || present('X') || present('F'))
        ) setflags("C");

        if (istty) setflags("q");

        if (SUPER_ID == 0 || present('a')) setflags("A");

        if (present('i')) field|= L_INODE;
        if (present('s')) field|= L_BLOCKS;
        if (present('M')) field|= L_MODE;
        if (present('X')) field|= L_EXTRA | L_MODE;
        if (present('t')) field|= L_BYTIME;
        if (present('u')) field|= L_ATIME;
        if (present('c')) field|= L_CTIME;
        if (present('l')) field|= L_MODE | L_LONG;
        if (present('g')) field|= L_MODE | L_LONG | L_GROUP;
        if (present('F')) field|= L_MARK;
        if (present('p')) field|= L_MARKDIR;
        if (present('D')) field|= L_TYPE;
        if (present('T')) field|= L_MODE | L_LONG | L_LONGTIME;
        if (present('d')) field|= L_DIR;
        if (present('h')) field|= L_KMG;
        if (field & L_LONG) field&= ~L_EXTRA;

#ifdef S_IFLNK
        status= present('L') ? stat : lstat;
#endif

        if (present('C')) {
                int t= istty ? 1 : open("/dev/tty", O_WRONLY);

                if (t >= 0 && ioctl(t, TIOCGWINSZ, &ws) == 0 && ws.ws_col > 0)
                        ncols= ws.ws_col - 1;

                if (t != 1 && t != -1) close(t);
        }

        depth= SURFACE;

        if (*argv == nil) {
                if (!(field & L_DIR)) depth= SURFACE1;
                pushfile(aflist, newfile("."));
        } else {
                if (argv[1] == nil && !(field & L_DIR)) depth= SURFACE1;

                do {
                        pushfile(aflist, newfile(*argv++));
                        aflist= &(*aflist)->next;
                } while (*argv!=nil);
        }
        listfiles(flist, depth,
                (field & L_DIR) ? BOTTOM : present('R') ? FLOATING : SINKING);
        return ex;
}

---