This is the job of the test command, which can check if a file exists and its type. Since only the check is completed, the test command sets the exit code to 0 or 1 (either false or true, respectively) whether the test is successful or not. The test command also has a logical "n...
How to check if a variable exists or is “null”? How to check if a file exists? How to check if a directory exists? How to check if a command succeeds or failed? How to do string comparison and check if a string equals to a value? How to check if a string is in an array?
而if [ ! -z err]||[!−eapk ]; then 没问题; 整数比较 : -eq 等于,如:if [ "a"−eq"b" ] -ne 不等于,如:if [ "a"−ne"b" ] -gt 大于,如:if [ "a"−gt"b" ] -ge 大于等于,如:if [ "a"−ge"b" ] -lt 小于,如:if [ "a"−lt"b" ] -le 小于等于,如:if...
including if, else, and elif. Then we'll look at a few of the "primary" operators you can leverage in a conditional statement such as = for string equality, -eq for numeric equality, and -e to check if a file exists. After that, we'll use conditional statements...
Navigate to a directory where your hello_world.sh is located and make the file executable: $ chmod +x hello_world.sh Now you are ready to execute your first bash script: ./hello_world.sh 2. Simple Backup bash shell script #!/bin/bash tar -czf myhome_directory.tar.gz /home/linuxconf...
The last two chapters have discussed how to use the bash shell. Bash itself is a little programming language, and this chapter we’re going to discuss how you can write your own computer programs in Bash. Programming in Bash is useful to know because of how seamlessly it integrates with al...
and elif. Then we'll look at a few of the "primary" operators you can leverage in a conditional statement such as = for string equality, -eq for numeric equality, and -e to check if a file exists. After that, we'll use conditional statements to create a function that asserts that ...
#!/bin/bashFILES="$@"for f in $FILESdo # if .bak backup file exists, read next file if [ -f ${f}.bak ] then echo "Skiping $f file..." continue # read next file and skip the cp command fi # we are here means no backup file exists, just use cp command to copy file /...
How to do a foreach loop in bash? How to do a do-while loop in bash? How to create an infinite loop in bash? How to find if a number is odd or even in bash? How to iterate over a bash array? How to loop over each line of a file? How to iterate over a list of files?
On lines 33-35, I wait for thescptask to finish, get the return code, and if it's an error, abort. On line 37, I check that the file could be parsed, otherwise, I exit with an error. So how does the error handling look now?