The tests below are test conditions provided by the shell:
* -b file = True if the file exists and is block special file.
* -c file = True if the file exists and is character special file.
* -d file = True if the file exists and is a directory.
* -e file = True if the file exists.
* -f file = True if the file exists and is a regular file
* -g file = True if the file exists and the set-group-id bit is set.
* -k file = True if the files’ “sticky” bit is set.
* -L file = True if the file exists and is a symbolic link.
* -p file = True if the file exists and is a named pipe.
* -r file = True if the file exists and is readable.
* -s file = True if the file exists and its size is greater than zero.
* -s file = True if the file exists and is a socket.
* -t fd = True if the file descriptor is opened on a terminal.
* -u file = True if the file exists and its set-user-id bit is set.
* -w file = True if the file exists and is writable.
* -x file = True if the file exists and is executable.
* -O file = True if the file exists and is owned by the effective user id.
* -G file = True if the file exists and is owned by the effective group id.
* file1 -nt file2 = True if file1 is newer, by modification date, than file2.
* file1 ot file2 = True if file1 is older than file2.
* file1 ef file2 = True if file1 and file2 have the same device and inode numbers.
* -z string = True if the length of the string is 0.
* -n string = True if the length of the string is non-zero.
* string1 = string2 = True if the strings are equal.
* string1 != string2 = True if the strings are not equal.
* !expr = True if the expr evaluates to false.
* expr1 -a expr2 = True if both expr1 and expr2 are true.
* expr1 -o expr2 = True is either expr1 or expr2 is true.
Shell中的数据问题
ArrayName=(”element 1″ “element 2″ “element 3″) #数组定义
echo ${#ArrayName[@]}
echo “The number of elements in the array is ${#ArrayName[*]}”
例子
#!/bin/bash
# define array
# name server names FQDN
NAMESERVERS=(”ns1.nixcraft.net.” “ns2.nixcraft.net.” “ns3.nixcraft.net.”)
# get length of an array
tLen=${#NAMESERVERS[@]}
# use for loop read all nameservers
for (( i=0; i<${tLen}; i++ ));
do
echo ${NAMESERVERS[$i]}
done
Sample output:
ns1.nixcraft.net.
ns2.nixcraft.net.
ns3.nixcraft.net.