[Linux 文章收集] BASH Shell: HowTo Create Empty Temporary Files Quickly

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Question 
Various methods exists to create a random temporary file name. This is useful if your application/shell scripting needs temporary unique file names. 

Method #1: Use of $RANDOM bash shell variable 
1) At shell prompt type command: 

# echo $RANDOM
1545

You will get random value every time. This variable can be use to create unique file name as below demonstration shell: 
- demo.sh 

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1. #!/bin/sh  
2.   
3. # Create unique file name  
4. UNIQUE_FILE_NAME="File_$RANDOM.txt"  
5. while [ -f "$UNIQUE_FILE_NAME" ];  
6. do  
7.     UNIQUE_FILE_NAME="File_$RANDOM.txt"  
8. done  
9.   
10. echo "test" > "$UNIQUE_FILE_NAME"  
11. echo "File '$UNIQUE_FILE_NAME' is unique!"  

Method # 2 Use of $$ variable 
This is old and classic method. $$ shell variable returns the current running process this can be use to create unique temporary file as demonstrated in following script: 
- demo2.sh 

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1. #!/bin/sh  
2. TFILE="/tmp/$(basename $0).$$.tmp"  
3. ls > $TFILE  
4. echo "See directory listing in $TFILE"  

Method # 3 Use of mktemp or tempfile utility 
As name suggest both makes unique temporary filename. Just type mktemp at shell prompt to create it: 

# mktemp // Create temple file
/tmp/tmp.erRDXG8krH
# test -f /tmp/tmp.erRDXG8krH && echo "Temp file created" // Confirm that the temple file being created
Temp file created

// -d, --directory: create a directory, not a file
# mktemp -d
/tmp/tmp.TfRrhIE4SZ
# test -d /tmp/tmp.TfRrhIE4SZ && echo "Temp dir created" // Confirm that the temple directory being created
Temp dir created
# ls -hl /tmp/

Supplement 
* Unix Special Variables