File test operators
Returns true if...
-e
file exists
-a
file exists
This is identical in effect to -e. It has been "deprecated," [1] and its use is discouraged.
-f
file is a regular file (not a directory or device file)
-s
file is not zero size
-d
file is a directory
-b
file is a block device
-c
file is a character device
-p
file is a pipe
-h
file is a symbolic link
-L
file is a symbolic link
-S
file is a socket
-t
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. [2] 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.
-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. [3] 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, she can only delete those files that she owns in it. 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).
integer comparison
-eq
is equal to
if [ "$a" -eq "$b" ]
-ne
is not equal to
if [ "$a" -ne "$b" ]
-gt
is greater than
if [ "$a" -gt "$b" ]
-ge
is greater than or equal to
if [ "$a" -ge "$b" ]
-lt
is less than
if [ "$a" -lt "$b" ]
-le
is less than or equal to
if [ "$a" -le "$b" ]
<
is less than (within double parentheses)
(("$a" < "$b"))
<=
is less than or equal to (within double parentheses)
(("$a" <= "$b"))
>
is greater than (within double parentheses)
(("$a" > "$b"))
>=
is greater than or equal to (within double parentheses)
(("$a" >= "$b"))
string comparison
=
is equal to
if [ "$a" = "$b" ]
==
is equal to
if [ "$a" == "$b" ]
This is a synonym for =.
!=
is not equal to
if [ "$a" != "$b" ]
This operator uses pattern matching within a [[ ... ]] construct.
<
is less than, in ASCII alphabetical order
if [[ "$a" < "$b" ]]
if [ "$a" \< "$b" ]
Note that the "<" needs to be escaped within a [ ] construct.
>
is greater than, in ASCII alphabetical order
if [[ "$a" > "$b" ]]
if [ "$a" \> "$b" ]
Note that the ">" needs to be escaped within a [ ] construct.
-z
string is null, that is, has zero length
-n
string is not null.
compound comparison
-a
logical and
exp1 -a exp2 returns true if both exp1 and exp2 are true.
-o
logical or
exp1 -o exp2 returns true if either exp1 or exp2 is true.
These are similar to the Bash comparison operators && and ||, used within double brackets.
[[ condition1 && condition2 ]]
The -o and -a operators work with the test command or occur within single test brackets.
Returns true if...
-e
file exists
-a
file exists
This is identical in effect to -e. It has been "deprecated," [1] and its use is discouraged.
-f
file is a regular file (not a directory or device file)
-s
file is not zero size
-d
file is a directory
-b
file is a block device
-c
file is a character device
-p
file is a pipe
-h
file is a symbolic link
-L
file is a symbolic link
-S
file is a socket
-t
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. [2] 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.
-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. [3] 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, she can only delete those files that she owns in it. 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).
integer comparison
-eq
is equal to
if [ "$a" -eq "$b" ]
-ne
is not equal to
if [ "$a" -ne "$b" ]
-gt
is greater than
if [ "$a" -gt "$b" ]
-ge
is greater than or equal to
if [ "$a" -ge "$b" ]
-lt
is less than
if [ "$a" -lt "$b" ]
-le
is less than or equal to
if [ "$a" -le "$b" ]
<
is less than (within double parentheses)
(("$a" < "$b"))
<=
is less than or equal to (within double parentheses)
(("$a" <= "$b"))
>
is greater than (within double parentheses)
(("$a" > "$b"))
>=
is greater than or equal to (within double parentheses)
(("$a" >= "$b"))
string comparison
=
is equal to
if [ "$a" = "$b" ]
==
is equal to
if [ "$a" == "$b" ]
This is a synonym for =.
!=
is not equal to
if [ "$a" != "$b" ]
This operator uses pattern matching within a [[ ... ]] construct.
<
is less than, in ASCII alphabetical order
if [[ "$a" < "$b" ]]
if [ "$a" \< "$b" ]
Note that the "<" needs to be escaped within a [ ] construct.
>
is greater than, in ASCII alphabetical order
if [[ "$a" > "$b" ]]
if [ "$a" \> "$b" ]
Note that the ">" needs to be escaped within a [ ] construct.
-z
string is null, that is, has zero length
-n
string is not null.
compound comparison
-a
logical and
exp1 -a exp2 returns true if both exp1 and exp2 are true.
-o
logical or
exp1 -o exp2 returns true if either exp1 or exp2 is true.
These are similar to the Bash comparison operators && and ||, used within double brackets.
[[ condition1 && condition2 ]]
The -o and -a operators work with the test command or occur within single test brackets.
Comments
Post a Comment
https://gengwg.blogspot.com/