shell文件存在的判断 shell数组

判断文件：

WORKDIR=/home/tmp
LOCAL_LIST_FILE=$WORKDIR/local.list

#if no local.txt file, generate a new one
if [ ! -f "$LOCAL_LIST_FILE" ]; then
touch $LOCAL_LIST_FILE
fi

注意：一定要有空格，判断文件是否存在，如果不存在，就生成一个新的

if [ ! -d /mnt ] # be sure the directory /mnt exists
then
mkdir /mnt
fi

目录。/mnt是否存在，不存在就生成目录/mnt


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.