Error logging patterns in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to redirect error messages to a log file.

Bash Scripting

command [1] error.log

Drag options to blanks, or click blank then click option'

A>

B>>

C2>

D2>>

Attempts:

3 left

💡 Hint

Common Mistakes

Using > instead of 2> redirects standard output, not errors.

Using >> appends output but may not redirect errors.

Using 2> redirects the standard error (stderr) to the specified file.

2fill in blank

medium

Complete the code to append error messages to a log file without overwriting it.

Bash Scripting

command [1] error.log

Drag options to blanks, or click blank then click option'

A>>

B2>

C>

D2>>

Attempts:

3 left

💡 Hint

Common Mistakes

Using 2> overwrites the file instead of appending.

Using >> appends standard output, not errors.

2>> appends standard error messages to the log file.

3fill in blank

hard

Fix the error in the code to redirect both standard output and error to the same log file.

Bash Scripting

command > log.txt [1] log.txt

Drag options to blanks, or click blank then click option'

A2>&1

B2>>

C2>

D2>&2

Attempts:

3 left

💡 Hint

Common Mistakes

Using 2> redirects error separately, not combined.

Using 2>&2 does nothing as it redirects error to itself.

2>&1 redirects standard error to the same place as standard output.

4fill in blank

hard

Fill both blanks to redirect standard output to a file and standard error to another file.

Bash Scripting

command [1] out.log [2] err.log

Drag options to blanks, or click blank then click option'

A>

B2>

C>>

D2>>

Attempts:

3 left

💡 Hint

Common Mistakes

Using 2>> for standard output is incorrect.

Using > for errors does not redirect error stream.

> redirects standard output, and 2> redirects standard error.

5fill in blank

hard

Fill all three blanks to redirect standard output to append to a file, standard error to append to another file, and combine both outputs to the console.

Bash Scripting

command [1] out.log [2] err.log [3]

Drag options to blanks, or click blank then click option'

A>>

B2>>

C2>&1

D| tee -a

Attempts:

3 left

💡 Hint

Common Mistakes

Using > instead of >> overwrites files.

Not using tee means output won't show on console.

>> appends standard output, 2>> appends standard error, and | tee -a shows output on console while appending.

Practice

1. What does the 2> operator do in a bash script?

easy

A. Redirects error messages to a file

B. Redirects standard output to a file

C. Appends output to a file

D. Runs a command in the background

Solution

1. Step 1: Understand bash output streams

   Bash has two main output streams: standard output (1) and standard error (2).

2. Step 2: Identify the meaning of 2>

   The operator 2> redirects the standard error stream to a file or location.

3. Final Answer:

   Redirects error messages to a file -> Option A

4. Quick Check:

   2> means error redirect [OK]

Hint: Remember 2 is error stream, so 2> redirects errors [OK]

Common Mistakes:

• Confusing 2> with > which redirects standard output
• Thinking 2> appends instead of overwriting
• Assuming 2> runs commands in background

2. Which of the following is the correct syntax to redirect only error messages (overwriting the file) to a file named error.log?

easy

A. command > error.log

B. command 2>> error.log

C. command &> error.log

D. command 2> error.log

Solution

1. Step 1: Understand redirection operators

   2> redirects standard error and overwrites the file; 2>> appends errors.

2. Step 2: Match requirement to syntax

   We want to redirect only errors and overwrite the file, so 2> error.log is correct.

3. Final Answer:

   command 2> error.log -> Option D

4. Quick Check:

   Use 2> for error overwrite [OK]

Hint: Use 2> to overwrite error file, 2>> to append [OK]

Common Mistakes:

• Using > which redirects standard output, not errors
• Using &> which redirects both output and errors
• Confusing append (>>) with overwrite (>)

3. What will be the output of the following command if script.sh prints "Success" to standard output and "Error occurred" to standard error?

./script.sh > output.log 2> error.log

medium

A. "Success" is saved in output.log, "Error occurred" in error.log

B. Both messages saved in output.log

C. Both messages appear on the terminal

D. "Error occurred" saved in output.log, "Success" in error.log

Solution

1. Step 1: Analyze redirection operators

   > output.log redirects standard output to output.log, 2> error.log redirects standard error to error.log.

2. Step 2: Match outputs to files

   "Success" goes to standard output, so saved in output.log; "Error occurred" goes to standard error, saved in error.log.

3. Final Answer:

   "Success" is saved in output.log, "Error occurred" in error.log -> Option A

4. Quick Check:

   Separate output and error files [OK]

Hint: Use > for output, 2> for errors to separate logs [OK]

Common Mistakes:

• Assuming both outputs go to same file
• Confusing 2> with >
• Expecting output on terminal despite redirection

4. Identify the error in this command intended to redirect errors to errors.log:

command 2>2 errors.log

medium

A. Should use &> instead of 2>

B. Missing space between command and 2>

C. Extra '2' causes errors to be redirected to file named '2' instead of 'errors.log'

D. No error, command is correct

Solution

1. Step 1: Examine the redirection syntax

   The correct syntax to redirect errors is 2> filename. Here, 2>2 errors.log redirects stderr to file 2, treating errors.log as a command argument.

2. Step 2: Identify the cause of error

   The extra '2' makes the filename 2 instead of errors.log.

3. Final Answer:

   Extra '2' causes errors to be redirected to file named '2' instead of 'errors.log' -> Option C

4. Quick Check:

   2> must be followed by correct filename [OK]

Hint: Check redirection target filename after 2> [OK]

Common Mistakes:

• Adding extra numbers or symbols in filename position
• Confusing &> with 2>
• Missing spaces causing parsing errors

5. You want to run a script and save both standard output and error messages into separate files, but also keep the error messages appended (not overwritten). Which command achieves this?

hard

A. ./script.sh > output.log 2> error.log

B. ./script.sh > output.log 2>> error.log

C. ./script.sh &> output.log

D. ./script.sh >> output.log 2> error.log

Solution

1. Step 1: Understand output and error redirection

   > overwrites standard output, 2>> appends standard error to a file.

2. Step 2: Match requirement to command

   We want output overwritten in output.log and errors appended in error.log, so ./script.sh > output.log 2>> error.log fits.

3. Final Answer:

   ./script.sh > output.log 2>> error.log -> Option B

4. Quick Check:

   Use 2>> to append errors [OK]

Hint: Use 2>> to append errors, > to overwrite output [OK]

Common Mistakes:

• Using 2> which overwrites error file
• Using &> which merges output and errors
• Appending output but overwriting errors