How do I know if script command was executed successfully?

Question

How do I know if script command was executed successfully?

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#1 by (5 votes)

1

I need the script to identify if the tar.gz file was successfully generated in an if. Here is a nonfunctional example:

VAR=tar -zcf teste.tar.gz teste/testeDir
if [VAR]
then
echo "Sucesso"
else
echo "Erro"
fi

Pretty simple I think but I could not do it! I await answers ...

bash shell

asked by anonymous 29.07.2016 / 20:14

1 answer

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score 5 · Accepted Answer

use the variable $? it returns "0" if the last command was successfully executed, and returns "1" if there was an error in this command.

Below is a table with these special variables that are available in the shell:

Variable Description

$ 0 Parameter number 0 (name of the command or function)
$ 1 Parameter number 1 (from the command line or function)
... Parameter number N of the command line or function)
$ 9 Parameter number 9 (from the command line or function)
$ {10} Parameter number 10 (from the command line or function)
$ # Total number of command line parameters or function
$ * All parameters, as a single string
$ @ All parameters, such as multiple protected strings
$$ PID of the current process (from the script itself)
$! PID of the last background process
$ _ Last argument of the last command executed
$? Return value of last executed command

See this example of the cat command in my terminal:

felix@asgard:[~]: cat escrever.py 
arq = open('arquivo.txt','w')
arq.write("Pyhton é legal")
arq.close()
felix@asgard:[~]: echo $?
0
felix@asgard:[~]: cat escreve.py 
cat: escreve.py: No such file or directory
felix@asgard:[~]: echo $?
1

In the example below I only put the "success" result because in my tests, when I tried to compress a non-existent file or even putting wrong arguments to compress, simply the command would not execute, thus 'breaking' the script:

#!/bin/bash

tar -zcf escrever.tar.gz escrever.py

if [ $? -eq 0 ]
then
    echo "sucesso"
fi