file (descriptor) is
associated with a terminal device
This test option may be used to check whether the
stdin ([ -t 0 ])
or stdout ([ -t 1 ])
in a given script is a terminal.
-r
file has read permission (for the
user running the test)
-w
file has write permission (for the user running
the test)
-x
file has execute permission (for the user running
the test)
-g
set-group-id (sgid) flag set on file or directory
If a directory has the sgid
flag set, then a file created within that directory belongs
to the group that owns the directory, not necessarily to
the group of the user who created the file. This may be
useful for a directory shared by a workgroup.
-u
set-user-id (suid) flag set on file
A binary owned by root
with set-user-id flag set
runs with root privileges, even
when an ordinary user invokes it.
[1]
This is useful for executables (such as
pppd and cdrecord)
that need to access system hardware. Lacking the
suid flag, these binaries could not
be invoked by a non-root user.
-rwsr-xr-t 1 root 178236 Oct 2 2000 /usr/sbin/pppd
A file with the suid flag set shows
an s in its permissions.
-k
sticky bit set
Commonly known as the "sticky bit," the
save-text-mode flag is a special
type of file permission. If a file has this flag set,
that file will be kept in cache memory, for quicker access.
[2]
If set on a directory, it restricts write permission.
Setting the sticky bit adds a t
to the permissions on the file or directory listing.
drwxrwxrwt 7 root 1024 May 19 21:26 tmp/
If a user does not own a directory that has the sticky
bit set, but has write permission in that directory,
he can only delete files in it that he owns. This keeps
users from inadvertently overwriting or deleting each
other's files in a publicly accessible directory, such
as /tmp.
(The owner of the directory or root
can, of course, delete or rename files there.)
-O
you are owner of file
-G
group-id of file same as yours
-N
file modified since it was last read
f1 -nt f2
file f1 is newer than
f2
f1 -ot f2
file f1 is older than
f2
f1 -ef f2
files f1 and
f2 are hard links to the same
file
!
"not" -- reverses the sense of the
tests above (returns true if condition absent).
Example 7-4. Testing for broken links
#!/bin/bash
# broken-link.sh
# Written by Lee bigelow <[email protected]>
# Used with permission.
#A pure shell script to find dead symlinks and output them quoted
#so they can be fed to xargs and dealt with :)
#eg. broken-link.sh /somedir /someotherdir|xargs rm
#
#This, however, is a better method:
#
#find "somedir" -type l -print0|\
#xargs -r0 file|\
#grep "broken symbolic"|
#sed -e 's/^\|: *broken symbolic.*$/"/g'
#
#but that wouldn't be pure bash, now would it.
#Caution: beware the /proc file system and any circular links!
##############################################################
#If no args are passed to the script set directorys to search
#to current directory. Otherwise set the directorys to search
#to the agrs passed.
####################
[ $# -eq 0 ] && directorys=`pwd` || directorys=$@
#Setup the function linkchk to check the directory it is passed
#for files that are links and don't exist, then print them quoted.
#If one of the elements in the directory is a subdirectory then
#send that send that subdirectory to the linkcheck function.
##########
linkchk () {
for element in $1/*; do
[ -h "$element" -a ! -e "$element" ] && echo \"$element\"
[ -d "$element" ] && linkchk $element
# Of course, '-h' tests for symbolic link, '-d' for directory.
done
}
#Send each arg that was passed to the script to the linkchk function
#if it is a valid directoy. If not, then print the error message
#and usage info.
################
for directory in $directorys; do
if [ -d $directory ]
then linkchk $directory
else
echo "$directory is not a directory"
echo "Usage: $0 dir1 dir2 ..."
fi
done
exit 0
