The only impact of exit 0 at the end of the script is to return 0 instead of the status from the previous instruction. Example: root@hostname [~] # echo -n hello helloroot@hostname [~] # I've always found that very annoying. Numeric and String Comparison. The bash scripting language uses this convention to mark the end of a complex expression, such as an if statement or case statement. If N is not given, the exit status code is that of the last executed command.. If offset evaluates to a number less than zero, the value is used as an offset from the end of the value of parameter. For example: All commands after this will be run as normal. [ -b FILE] True if FILE exists and is a block-special file. If parameter is @, the result is length positional parameters beginning at offset. Most of the time the output of a command ends with the newline character. Using test or [with the predicate -d is of value here. (*.txt) to match all names not ending with .txt), it enables glob patterns to match hidden names, and it makes the pattern expand to nothing at all if nothing matches. In programming, conditions are crucial : they are used to assert whether some conditions are true or not.. echo 'odd' –» it prints “odd” to your screen fi –» end of the if statement. if [ -z $1 ] then echo "sorry you didn't give me a value" exit 2 fi If value is not true. End every if statement with the fi statement. The backslash escapes the special meaning to make it a normal plain single quote again. [ -g FILE] True if FILE exists and its SGID bit is set. Line 8 - fi signals the end of the if statement. If a script ends with exit 0, it will exit with the code 0 only if that last instruction was executed. Usually though in a bash script you want to check if the argument is empty rather than if it is not empty, to do this you can use the -z operator. [ -e FILE] True if FILE exists. [ -f FILE] True if FILE exists and is a regular file. – Gilles 'SO- stop being evil' Sep 6 '16 at 22:08 If that is a fair assessment, then I would recommend testing the string to see if it does refer to a directory or not. When used in shell scripts, the value supplied as an argument to the exit command is returned to the shell as an exit code.. [ -c FILE] True if FILE exists and is a character-special file. Line 6 - The backslash ( \ ) in front of the single quote ( ' ) is needed as the single quote has a special meaning for bash and we don't want that special meaning. The -z operator is the opposite of -n, you could get the same results by performing this if statement with the ! The following example sets a variable and tests the value of the variable using the if statement. When working with Bash and shell scripting, you might need to use conditions in your script.. The shell options set on the first line will make the bash shell enable extended globbing patterns (! The then statement is placed on the same line with the if. Bash check if process is running or not. But sometimes it does not, so the next shell prompt is printed in the same line together with the output. Okay, save your bash script, give permission with … The echo statement prints its argument, in this case, the value of the variable count, to the terminal window. Primary Meaning [ -a FILE] True if FILE exists. [ -d FILE] True if FILE exists and is a directory. ; pidof command – Find the process ID of a running program on Linux or Unix-like system; ps command – Get information about the currently running Linux or Unix processes, including … Bash commands to check running process: pgrep command – Looks through the currently running bash processes on Linux and lists the process IDs (PID) on screen. @Hatclock No, not at all. 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