File modification time (seconds) on Unix

Question

Hi there,

On Unix, is there a command to display a file's modification time, precise to the second?

On Linux this is easily done with a "stat -c %y", which returns something like 2009-11-27 11:36:06.000000000 +0100. I found no equivalent on Unix.

Answer 1

According to the man page on my Mac (which has the BSD standard version of stat) you can get the epoch time version of the modification in seconds with:

stat -f %m /etc/passwd

Or if you want to print that out in hours:mins:secs you can do this:

perl -e "print scalar(localtime(`stat -f %m /etc/passwd`))"

Answer 2

For anyone facing the same issue, I found no solution (on HP-UX 11i anyway). Ended up coding a personalized "ls -lh" for my needs. It's not that hard.. Prints something like :

 - 664 rw-/rw-/r--   1L expertNoob adm   8.37 kB 2010.08.24 12:11:15 findf1.c
 d 775 rwx/rwx/r-x   2L expertNoob adm     96 B  2010.08.24 15:17:37 tmp/
 - 775 rwx/rwx/r-x   1L expertNoob adm     16 kB 2010.08.24 12:35:30 findf1
 - 775 rwx/rwx/r-x   1L expertNoob adm     24 kB 2010.09.14 19:45:20 dir_info
 - 444 r--/r--/r--   1L expertNoob adm   9.01 kB 2010.09.01 11:23:41 getopt.c
 - 664 rw-/rw-/r--   1L expertNoob adm   6.86 kB 2010.09.01 11:24:47 getopt.o
 - 664 rw-/rw-/r--   1L expertNoob adm   6.93 kB 2010.09.14 19:37:44 findf1.o
 l 775 rwx/rwx/r-x   1L expertNoob adm      6 B  2010.10.06 17:09:01 test1 -> test.c
 - 664 rw-/rw-/r--   1L expertNoob adm    534 B  2009.03.26 15:34:23 > test.c
 d 755 rwx/r-x/r-x  25L expertNoob adm      8 kB 2009.05.20 15:36:23 zip30/

Here it is :

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/errno.h>
#include <dirent.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>
#include <locale.h>
#include <langinfo.h>
#include <stdio.h>
//#include <stdint.h>
#include <limits.h> // PATH_MAX
#include <stdarg.h>
#include "getopt.h"

static short START_VSNBUFF=16;
// This is bformat from Better String library (bstrlib), customized
int strformat (char ** str, const char * fmt, ...) {

    va_list arglist;
    char * buff;
    int n, r;

    /* Since the length is not determinable beforehand, a search is
       performed using the truncating "vsnprintf" call (to avoid buffer
       overflows) on increasing potential sizes for the output result. */

    if ((n = (int) (2*strlen (fmt))) < START_VSNBUFF) n = START_VSNBUFF;
    if ( NULL == ( buff = (char *) malloc((n + 2)*sizeof(char)) ) ) {
        n = 1;
        if ( NULL == ( buff = (char *) malloc((n + 2)*sizeof(char)) ) ) {
            fprintf( stderr, "strformat: not enough memory to format string\n" );
            return -1;
        }
    }

    for (;;) {
        va_start (arglist, fmt);
        r = vsnprintf (buff, n + 1, fmt, arglist); // n+1 chars: buff[0]..buff[n], n chars from arglist: buff[n]='\0'
        va_end (arglist);

        buff[n] = (unsigned char) '\0'; // doesn't hurt, especially strlen!

        if ( strlen(buff) < n ) break;

        if (r > n) n = r; else n += n;

        if ( NULL == ( buff = (char *) realloc( buff, (n + 2)*sizeof(char) ) ) ) {
            free(buff);
            fprintf( stderr, "strformat: not enough memory to format string\n" );
            return -1;
        }
    }

    if( NULL != *str ) free(*str);
    *str = buff;
    return 0;
}

int printFSObjectInfo( const char * path, const char * name ) {

    struct stat    statbuf;

    struct passwd *pwd;
    struct group  *grp;
    struct tm     *tm;
    char           datestring[256];
    char           *type = "? ";
    char           *fbuf = NULL;

    double         size = 0;
    const char     *units[] = {"B ", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"};
    int            i = 0;

    char owner[] = "---", group[] = "---", others[] = "---";


    /* Get entry's information. */
    if ( -1 == lstat( path, &statbuf ) ) {
        fprintf( stderr, "printFSObjectInfo: error: can't stat %s\n", path );
        if( 0 == strformat( &fbuf, "lstat() said: %s", path ) ) { perror(fbuf); return -1; }
    }

    // File type
    if( S_ISREG(statbuf.st_mode) ) type = "-"; // regular file
    if( S_ISDIR(statbuf.st_mode) ) {         // directory
        type="d";
        if( S_ISCDF(statbuf.st_mode) ) type = "hd";  // hidden dir
    }
    if( S_ISBLK(statbuf.st_mode) ) type = "b"; // block special
    if( S_ISCHR(statbuf.st_mode) ) type = "c"; // character special
    if( S_ISFIFO(statbuf.st_mode) ) type = "f"; // pipe or FIFO
    if( S_ISLNK(statbuf.st_mode) ) type = "l"; // symbolic link
    if( S_ISSOCK(statbuf.st_mode) ) type = "s"; // socket
    if( S_ISNWK(statbuf.st_mode) ) type = "n"; // network special
    printf( "%2s ", type );

    /* Print out type, permissions, and number of links. */
    //printf("%10.10s", sperm (statbuf.st_mode));
    if( S_IRUSR & statbuf.st_mode ) owner[0] = 'r';
    if( S_IWUSR & statbuf.st_mode ) owner[1] = 'w';
    if( S_IXUSR & statbuf.st_mode ) owner[2] = 'x';

    if( S_IRGRP & statbuf.st_mode ) group[0] = 'r';
    if( S_IWGRP & statbuf.st_mode ) group[1] = 'w';
    if( S_IXGRP & statbuf.st_mode ) group[2] = 'x';

    if( S_IROTH & statbuf.st_mode ) others[0] = 'r';
    if( S_IWOTH & statbuf.st_mode ) others[1] = 'w';
    if( S_IXOTH & statbuf.st_mode ) others[2] = 'x';

    //printf( "\n%o\n", statbuf.st_mode );
    printf( "%3o %s/%s/%s ", 0777 & statbuf.st_mode, owner, group, others );

    printf("%4dL", statbuf.st_nlink);

    /* Print out owner's name if it is found using getpwuid(). */
    if ((pwd = getpwuid(statbuf.st_uid)) != NULL)
        printf(" %-8.8s", pwd->pw_name);
    else
        printf(" %-8d", statbuf.st_uid);

    /* Print out group name if it is found using getgrgid(). */
    if ((grp = getgrgid(statbuf.st_gid)) != NULL)
        printf(" %-8.8s", grp->gr_name);
    else
        printf(" %-8d", statbuf.st_gid);

    /* Print size of file. */
    //printf(" %9d", (int)statbuf.st_size);
    i = 0;
    size = (double) statbuf.st_size;
    while (size >= 1024) {
        size /= 1024;
        i++;
    }
    if( 0 == (double)(size - (long) size) )
         printf( "%7d %-2s",  (long)size, units[i] );
    else printf( "%7.2f %-2s", size, units[i] );

    tm = localtime(&statbuf.st_mtime);

    /* Get localized date string. */
    strftime(datestring, sizeof(datestring), "%Y.%m.%d %T", tm); // nl_langinfo(D_T_FMT)

    if ( 0 == strcmp(name, "\n") )
         printf(" %s > %s", datestring, path);
    else {
        if( 0 == strcmp(type, "d") ) printf(" %s %s/", datestring, name);
        else                         printf(" %s %s", datestring, name);
    }

    if( 0 == strcmp(type, "l") ) {
        char buf[1+PATH_MAX];
        if( -1 == readlink( path, buf, (1+PATH_MAX) ) ) {
            fprintf( stderr, "printFSObjectInfo: error: can't read symbolic link %s\n", path);
            if( 0 == strformat( &fbuf, "readlink() said: %s:", path ) ) { perror(fbuf); return -2; }
        }
        else {
            lstat( buf, &statbuf ); // want errno, a symlink may point to non-existing object
            if(errno == ENOENT) printf(" -> %s [!no such file!]\n", buf );
            else {
                printf(" -> %s\n", buf );
                if ( 0 != strcmp(name, "\n") ) printFSObjectInfo( buf, "\n" );
            }
        }
    }
    else printf("\n");

    return 0;
}

int main(int argc, char **argv) {

    struct dirent *dp;
    struct stat    statbuf;

    char           *path = NULL; //[1+PATH_MAX];
    char           *fbuf = NULL;
    char           *pathArg = NULL;

    if( argc == 1 || 0 == strlen(argv[1]) ) pathArg = ".";
    else pathArg = argv[1];

    if ( lstat( pathArg, &statbuf ) == -1 ) {
        printf("%s: error: can't stat %s\n", argv[0], pathArg);
        if( 0 == strformat( &fbuf, "stat() said: %s", pathArg ) ) perror(fbuf);
        exit(2);
    }

if( S_ISDIR(statbuf.st_mode) ) {
    DIR *dir = opendir( pathArg );
    if( NULL == dir ) {
        fprintf( stderr, "%s: error: can't open %s\n", argv[0], pathArg );
        if( 0 != strformat( &fbuf, "opendir() said: %s", pathArg ) ) exit(5);
        perror(fbuf);
        exit(4);
    }

    /* Loop through directory entries. */
    while ( (dp = readdir(dir)) != NULL ) {

        if( 0!= strformat( &path, "%s/%s", pathArg, dp->d_name ) ) continue;

        printFSObjectInfo( path, dp->d_name );
    }
    closedir(dir);
} else  printFSObjectInfo( pathArg, pathArg );

    return 0;
}

In printFSObjectInfo() you have full functionality of lstat() system call, you can customize this to your wishes.

Be well.