Collection of Tools & Utilities/Collection of Tools and Utilities.iso/tex/miscnix.zip/TAIL.C

Text File | 1988-05-28 | 5KB | 208 lines

#include <stdio.h>
#define    ERROR    0
#define    MAXINT    32767
#define    CPMEOF    26    /* Control Z */

/**    TAIL    Print last several lines of a file.

    Usage:    tail [-|+n[lbc][r]] [file ...]
        where n is the number of lines (l), 512 byte blocks (b), or
        characters (c) from the beginning (+) or end (-) of the file.
        The 'r' option causes the lines to be printed in reverse order.
        Default is -10 (or -32767 if 'r' is set).

        One or more files may be given; also, standard input will be
        included in the list if it is a pipe or file.  If more than one
        file is given, the files will be separated by lines of the form:
            ==> file.nam <==

    Note:    If you want to recompile this, make sure your C library allows
        you to do fseek() on stdin.

    No copyright, dammit:  this is PUBLIC DOMAIN!!!
*/

char    plus;
long    numarg;
char    unit    ='l';
char    revmode;

#define    BUFLEN    512
char    buf[BUFLEN];
#define    BUFLEN2    512
char    buf2[BUFLEN2];
char    *bufpos,*bufend;

long    ftell();
long    bgnpos;
long    filepos;

usage() {
    puts("Usage:  tail [-|+#[lbc][r]] [file ...]");
    puts("where # is the number of lines from the back (or front) of the file");
    puts("and the file is standard input by default.");
    exit(1);
}

readback(f)
    FILE *f; {
    int    len;

    len=BUFLEN;
    if (bgnpos>filepos-len) len=filepos-bgnpos;
    filepos-=len;
    fseek(f,filepos,0);
    fread(buf,1,len,f);
    bufpos=bufend= &buf[len];
}

processfile(f,s,b)
    FILE *f;
    char *s;    /* file name */
    int b; {    /* >0 if we want to print it */
    long    lastpos;
    int    nlines;
    int    len;

    if (b>0) {fputs("==> ",stdout); fputs(s,stdout); puts(" <==");}
    bgnpos=0;

    if (plus) {    /* if plus, make use of that information */
        bgnpos=numarg;
        if (unit!='c') {
        bufpos=bufend= &buf;
        nlines=numarg;
        while (nlines>0) {
            bufpos=strnchr(bufpos,bufend-bufpos,'\n');
            if (bufpos<bufend) {
            --nlines;
            ++bufpos;
            } else {
            bufpos= &buf;
            bufend= &buf[fread(buf,1,BUFLEN,f)];
            if (bufend<=bufpos) break;
            }
        }
        bgnpos=ftell(f) - (int) (bufend-bufpos);
        } /* end if unit */
    }
    else if (unit=='c') {
        fseek(f,0L,2);
        bgnpos=ftell(f)-numarg;
        if (bgnpos<0) bgnpos=0;
    }

    nlines=0;
    if (!plus && unit!='c') nlines=numarg;
    else if (revmode) nlines=MAXINT;

    /* go reversely through the file */

    if (nlines) {
        fseek(f,0L,2);
        filepos=ftell(f);
        readback(f);
        if (bufpos > &buf && *(bufpos-1)==CPMEOF) --bufpos;
        if (bufpos > &buf && *(bufpos-1)=='\n') --bufpos;
        do {
        lastpos=filepos + (int) (bufpos-&buf);
        for (;;) {
            bufpos=strrnchr(&buf,bufpos-&buf,'\n');
            if (bufpos>=&buf) break;
            readback(f);
            if (bufpos<=&buf) {nlines=0; bufpos= &buf-1; break;}
        }
        if (revmode) {
            len = (int) (lastpos-filepos) - (bufend-&buf);
            if (len <= 0) {
            if (*(bufend+len-1)=='\r') --len;
            fwrite(bufpos+1,1,len+bufend-bufpos-1,stdout);
            } else {
            fwrite(bufpos+1,1,bufend-bufpos-1,stdout);
            fseek(f,filepos + (int) (bufend-&buf),0);
            while (len>BUFLEN2) {
                fread(buf2,1,BUFLEN2,f);
                fwrite(buf2,1,BUFLEN2,stdout);
                len-=BUFLEN2;
            }
            fread(buf2,1,len,f);
            if (buf2[len-1]=='\r') --len;
            fwrite(buf2,1,len,stdout);
            }
            putchar('\n');
        }
        } while (--nlines > 0);
        bgnpos=filepos + (int) (bufpos-&buf+1);
    } /* end if */

    if (revmode) return;

    /* print the requested number of lines */

    fseek(f,bgnpos,0);
    for (;;) {
        /*fgets(buf,BUFLEN-1,f); len=strlen(buf);*/
        len=fgetss(buf,BUFLEN-1,f);
        if (len<0) break;
        if (len<BUFLEN-2) {    /* if end of line found */
        buf[len++]='\r';
        buf[len++]='\n';
        }
        fwrite(buf,1,len,stdout);    /* faster than puts */
    }
}

main(argc,argv)
    int argc;
    char **argv; {
    int    arg0    =1;
    int    arg;
    FILE    *f;
    char    c, *s;

    /* parse numeric argument */

    if (argc>1 && (argv[1][0]=='-' || (argv[1][0]=='+' && ++plus))) {
        s=argv[1]+1;
        c=*s;
        if (isdigit(c)) {
        while (isdigit(c)) {
            numarg=numarg*10+(c-'0');
            c= *++s;
        }
        unit=c;
        if (c=='b') {numarg<<=9; unit='c';}
        else if (c!='c' && c!='l') --s;
        ++s;
        }
        if (*s == 'r') {++s; ++revmode;}
        if (*s) usage();
        ++arg0;
    }
    if (numarg==0) {plus=0; numarg=(revmode? MAXINT: 10);}

    arg=arg0;
    --argc;

    if (!isatty(0)) {
        --arg0;
        processfile(stdin,"Standard input",argc-arg0);
    }

    if (arg0>argc) usage();

    for (; arg <= argc; ++arg) {
        if (arg>arg0) putchar('\n');
        /* Open file for input */
        s=argv[arg];
        f=fopen(s,"r");
        if (f==ERROR) {
        fputs("Cannot open ",stderr);
        fputs(s,stderr);
        fputs("\n",stderr);
        exit(1);
        }
        processfile(f,s,argc-arg0);
    }
}