Add Newline at the End of curl Response Body

1. Overview

When fetching web resources using curl, a missing trailing newline in the response body can cause the shell prompt to appear in the middle of the line. This minor but recurrent issue impairs legibility and command-line interaction, particularly when modifying or reissuing commands. While curl returns data exactly as received, some servers remove the final newline, leaving the terminal in an odd condition.

In this tutorial, we’ll discuss practical ways to automatically append a newline to curl responses, ensuring consistent shell behavior.

2. Using curl’s -w Option

The most direct and efficient way to add a trailing newline to a curl response is to use the built-in -w (write-out) flag. This solution doesn’t require any additional tools or instructions, making it outstanding for scripts and interactive applications where simplicity and cleanliness are important:

$ curl -s -w '\n' jsonip.com

{"ip":"10.10.10.10"}'

[root@localhost ~]#

In this example, the -w ‘\n’ flag tells curl to add a newline character at the end of the response body. The -s (silent) flag suppresses progress meters and error warnings, leaving only the raw response and the newline character shown. Furthermore, unlike approaches that need piping to external programs such as echo or sed, this solution runs entirely within curl, reducing overhead and dependencies.

Finally, the -w flag works dependably on Unix/Linux and macOS because modern curl versions are consistent on these platforms. In Windows, the -w flag works in Unix-like environments (e.g., WSL), but native PowerShell or CMD need curl installation.

3. Using echo

The echo command can be used to add a trailing newline to the output of a curl request, causing the shell prompt to return to the terminal’s left edge. Unlike approaches that edit curl‘s output directly, this solution runs curl and echo successively, always adding a newline after the response body:

$ curl jsonip.com; echo

{"ip":"10.10.10.10"}
[root@localhost ~]#

In this example, curl jsonip.com retrieves the server response, which in this case lacks a trailing newline. The semicolon guarantees that echo is executed immediately after curl completes, appending a newline to the output. This causes the shell prompt to start on a new line.

Additionally, Linux shells handle echo consistently, but macOS’s BSD-derived echo ignores flags such as -e, making it less flexible. Windows PowerShell’s echo alias (Write-Output) automatically appends a newline, but CMD’s echo requires manual JSON escaping.

4. Using printf

The printf command provides precise control over output formatting, making it a viable alternative to echo when attaching a trailing newline to curl responses. Unlike echo, printf does not append a newline unless expressly told, ensuring consistency between shells and input formats. This method is ideal for situations where dependability and consistency are needed:

$ curl -s jsonip.com; printf '\n'

{"ip":"10.10.10.10"}
[root@localhost ~]#

In this example, curl -s jsonip.com retrieves the response in silent mode, removing progress meters and errors. The semicolon guarantees that printf ‘\n’ runs after curl finishes, adding a newline character to the output. This ensures that the shell prompt always begins with a new line, regardless of whether the original response contained a trailing newline.

In addition, printf avoids the inconsistencies associated with echo (for example, unintended interpretation of escape sequences or arguments beginning with –). It adds the newline unconditionally, similar to curl‘s -w parameter, but does not edit the raw response body. This makes it safer to process responses that include special characters or formatting.

Finally, POSIX compatibility ensures that the printf command works consistently across Unix/Linux and macOS. In Windows, it works in WSL or Git Bash, but it requires changes in native PowerShell, where Write-Host or string interpolation may be preferable.

5. Using sed

The sed command allows for precise text output modification, including adding a trailing newline if one is missing. Moreover, we use this method for large responses and avoid redundant newlines. Thus, we use it mostly in situations where maintaining the original response structure is needed:

$ curl -s jsonip.com | sed '$a\'

{"ip":"10.10.10.10"}
[root@localhost ~]#

In this example, the sed ‘$a\’ command processes the curl output and adds a newline to the last line of the response. The a\ command in sed appends text after the specified line. The trailing backslash escapes the implied newline that sed supplies, ensuring the command appends only one newline if the response lacks one.

Additionally, GNU sed allows commands like sed ‘$a\’ out of the box, whereas macOS’s BSD sed requires explicit syntax (e.g., sed -e ‘$a\’) to insert newlines. If we’re using Windows, we must use GNU sed via WSL or Git Bash, as PowerShell lacks native sed support.

6. Using awk

The awk command provides a flexible, condition-based mechanism for appending a trailing newline to a curl response when missing. Moreover, this approach is useful for dealing with multi-line outputs or servers that utilize trailing newlines inconsistently, as it keeps the shell prompt intact while preserving the original response structure:

$ curl -sL jsonip.com | awk '1; END { if (NR>0 && $0 != "") print "" }'

{"ip":"10.10.10.10"}

[root@localhost ~]#

In this example, we start with curl -sL, where the -L argument makes sure curl follows any HTTP redirects. This is an important step if the target URL goes to another endpoint. The -s switch disables progress meters and errors, resulting in clean output. We then route the output to awk, which parses the response line by line.

Furthermore, our awk script has two sections. In the first section, 1; is a shorthand for printing each line as it appears. Also, in the second section, the END block runs after all input lines have been processed. Here, NR>0 ensures that the block runs only if there is at least one line of input, and $0!= “” validates that the last line is not empty. If the last line does not contain a trailing newline, print “” adds a newline to the output.

In addition, the awk command is compatible with Linux and macOS, although macOS’s BSD awk may lack several GNU extensions. However, our awk script behaves the same on both. Windows requires gawk in Unix-like settings since native PowerShell and CMD omit built-in awk.

7. Conclusion

Adding a trailing newline to curl responses ensures a clean terminal experience, especially when servers omit the character.

In this article, we’ve investigated several approaches to accomplish this. We talked about using echo for simplicity, printf for dependability, sed for efficient stream editing, and awk for dealing with multi-line or inconsistent outputs. Furthermore, we use printf ‘\n’ for most cases because it’s consistent and avoids edge cases. Tools like sed or awk provide flexibility for complex scenarios.

Finally, these techniques can help us avoid misaligned shell prompts and keep command-line workflows readable.