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Top Forums Programming read() without changing atime ? Post 302113178 by tantric on Wednesday 4th of April 2007 03:25:16 AM
Old 04-04-2007
read() without changing atime ?

Hey,

First of all I want to know How do I see the atime of a file ?? Whats the command ??

I think ls -l shows the last modified time right ? Because when I use cat to read a file, the timestamp shown by ls -l does not change.

Its not ls -lu ! man ls did not help ! How do I see the last access time of a file in unix ???

Now my next question is:

My C program reads a file using read(). But I do not want the last access time of the file to change. So, I am using utime() to update the atime and mtime of the file back to what it was before the read.

But the problem, the update will fail if the program does not have write permissions on the file. If the file is read only, the program will not be able to modify its attributes (am I right ?).

can you guys please help me out here Smilie

thanks,
Varun
 

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TMPWATCH(8)                                                System Administrator's Manual                                               TMPWATCH(8)

NAME
tmpwatch - removes files which haven't been accessed for a period of time SYNOPSIS
tmpwatch [-u|-m|-c] [-MUadfqstvx] [--verbose] [--force] [--all] [--nodirs] [--nosymlinks] [--test] [--fuser] [--quiet] [--atime|--mtime|--ctime] [--dirmtime] [--exclude path] [--exclude-user user] time dirs DESCRIPTION
tmpwatch recursively removes files which haven't been accessed for a given time. Normally, it's used to clean up directories which are used for temporary holding space such as /tmp. When changing directories, tmpwatch is very sensitive to possible race conditions and will exit with an error if one is detected. It does not follow symbolic links in the directories it's cleaning (even if a symbolic link is given as its argument), will not switch filesystems, skips lost+found directories owned by the root user, and only removes empty directories, regular files, and symbolic links. By default, tmpwatch dates files by their atime (access time), not their mtime (modification time). If files aren't being removed when ls -l implies they should be, use ls -u to examine their atime to see if that explains the problem. If the --atime, --ctime or --mtime options are used in combination, the decision about deleting a file will be based on the maximum of these times. The --dirmtime option implies ignoring atime of directories, even if the --atime option is used. The time parameter defines the threshold for removing files. If the file has not been accessed for time, the file is removed. The time argument is a number with an optional single-character suffix specifying the units: h for hours, d for days. If no suffix is specified, time is in hours. Following this, one or more directories may be given for tmpwatch to clean up. OPTIONS
-u, --atime Make the decision about deleting a file based on the file's atime (access time). This is the default. Note that the periodic updatedb file system scans keep the atime of directories recent. -m, --mtime Make the decision about deleting a file based on the file's mtime (modification time) instead of the atime. -c, --ctime Make the decision about deleting a file based on the file's ctime (inode change time) instead of the atime; for directories, make the decision based on the mtime. -M, --dirmtime Make the decision about deleting a directory based on the directory's mtime (modification time) instead of the atime; completely ignore atime for directories. -a, --all Remove all file types, not just regular files, symbolic links and directories. -d, --nodirs Do not attempt to remove directories, even if they are empty. -f, --force Remove files even if root doesn't have write access (akin to rm -f). -l, --nosymlinks Do not attempt to remove symbolic links. -q, --quiet Report only fatal errors. -s, --fuser Attempt to use the "fuser" command to see if a file is already open before removing it. Not enabled by default. Does help in some circumstances, but not all. Dependent on fuser being installed in /sbin. Not supported on HP-UX or Solaris. -t, --test Don't remove files, but go through the motions of removing them. This implies -v. -U, --exclude-user=user Don't remove files owned by user, which can be an user name or numeric user ID. -v, --verbose Print a verbose display. Two levels of verboseness are available -- use this option twice to get the most verbose output. -x, --exclude=path Skip path; if path is a directory, all files contained in it are skipped too. If path does not exist, it must be an absolute path that contains no symbolic links. SEE ALSO
cron(1), ls(1), rm(1), fuser(1) WARNINGS
GNU-style long options are not supported on HP-UX. AUTHORS
Erik Troan <ewt@redhat.com> Preston Brown <pbrown@redhat.com> Nalin Dahyabhai <nalin@redhat.com> Miloslav Trmac <mitr@redhat.com> 4th Berkeley Distribution Fri Dec 14 2007 TMPWATCH(8)
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