Running Multiple curl cmd Commands Found in a Separate .txt File in a Single Folder

To execute multiple curl commands stored in a text file, you must parse the file line by line and evaluate each entry as a shell command. The most robust method involves using a while read loop combined with eval, which allows you to handle complex arguments, spaces, and quotes correctly within your batch operations.

Preparing the Command File

The foundation of this automation is the structure of your input file. Whether you are on Windows using Command Prompt or macOS/Linux using Bash, the text file must contain one complete curl command per line. It is critical that the syntax is valid for the shell environment you intend to use. If you are working in a Unix-like environment (Bash/Zsh), ensure that any special characters like spaces or parentheses are properly quoted within the file itself. For example, a line might look like curl -o "file name.txt" https://example.com/data. This ensures that when the script reads the line, it treats the filename as a single argument rather than splitting it into separate tokens. In contrast, if you are strictly using Windows CMD, the parsing capabilities are more limited. You cannot easily embed quotes in the same way. Instead, you should avoid filenames with spaces or use short 8.3 names if necessary. However, the approach described below assumes a POSIX-compliant shell (like Git Bash on Windows or native Terminal on Mac) because handling complex curl arguments in pure CMD is error-prone and often requires workarounds like temporary batch files.

The Bash Scripting Approach

For users on Linux, macOS, or those using Git Bash on Windows, the standard solution is a simple shell script. Create a new file named run_curls.sh and open it in your preferred text editor. Inside this file, you will define the path to your directory containing the command list. Let's assume your folder is located at /path/to/commands and the file is named requests.txt. The core logic relies on reading the file line by line. You can achieve this using the while loop construct. The command read -r line reads each line into the variable line, preserving backslashes due to the -r flag. To execute the content of that variable as a command, you use the eval builtin. This function takes the string stored in line and passes it to the shell for execution as if you had typed it directly into the terminal. Here is the essential structure of the script:

#!/bin/bash

# Define the path to your directory and file
DIR="/path/to/your/folder"
FILE="$DIR/requests.txt"

# Check if the file exists
if [ ! -f "$FILE" ]; then
    echo "Error: File $FILE not found."
    exit 1
fi

# Read the file line by line
while IFS= read -r line || [[ -n "$line" ]]; do
    # Skip empty lines
    if [ -z "$line" ]; then
        continue
    fi
    
    # Execute the command
    eval "$line"
    
done < "$FILE"

echo "All commands completed."

This script handles several edge cases. The IFS= prefix prevents leading and trailing whitespace from being stripped from your command. The || [[ -n "$line" ]] part ensures that the last line of the file is processed even if it does not end with a newline character, which is a common source of bugs in shell scripting.

Handling Windows CMD Limitations

If you are restricted to the native Windows Command Prompt (cmd.exe), the eval equivalent is not available. Attempting to run for /f loops with complex arguments often fails when quotes are involved. A safer, albeit less elegant, method for CMD is to convert the text file into a batch file dynamically. You can use a PowerShell one-liner to iterate through the text file and generate a new execute.bat file. Then, you simply run that batch file. Alternatively, if your commands are simple and contain no spaces or special characters, you can use a basic FOR loop:

FOR /F "tokens=* USEBACKQ" %%F IN (`type requests.txt`) DO (
    CALL %%F
)

However, note that CALL expects a label or another batch file, not a raw command string with arguments in the same way Bash handles it. Therefore, for Windows users, it is highly recommended to install Git Bash or WSL (Windows Subsystem for Linux) and use the Bash script provided in the previous section. This avoids the pitfalls of CMD's rigid parsing rules.

Security and Error Handling Considerations

Using eval introduces security risks if the source file is untrusted. Since eval executes any valid shell code, a malicious line could delete files or exfiltrate data. Always ensure that requests.txt is generated by a trusted source or manually verified before running the script. Additionally, consider adding error checking. If one curl command fails, the default behavior of this script is to continue to the next line. If you want the script to stop immediately upon any failure, you can add set -e at the top of your Bash script. This causes the script to exit if any command returns a non-zero status code. Conversely, if you want to log errors, you can redirect stderr to a log file: eval "$line" >> output.log 2>&1.

Optimizing for Performance

When dealing with hundreds of URLs, sequential execution can be slow. While this tutorial focuses on simplicity, you might later explore parallel execution tools like xargs or GNU parallel. These tools allow you to split the workload across multiple CPU cores, significantly reducing the total time required to process large lists of HTTP requests. However, for most moderate-sized batches, the sequential while loop provides sufficient performance and easier debugging capabilities.

Frequently Asked Questions

Why does my curl command fail when copied from a browser?

Copied commands often contain invisible formatting characters or incorrect quote types (smart quotes vs. straight quotes). Always paste the command into a plain text editor first to ensure it uses standard ASCII characters before saving it to your .txt file.

Can I run these commands in parallel instead of sequentially?

Yes, but it requires a different approach. You would typically use xargs -P or GNU parallel to distribute the commands across multiple processes. This speeds up execution but makes debugging individual failures more difficult.

How do I handle authentication headers in the text file?

You can include -H "Authorization: Bearer token" directly in the line within the text file. Ensure the entire header string is enclosed in double quotes inside the file so that eval passes it correctly to curl without breaking the argument structure.

What happens if one curl request times out?

By default, the script will wait for the timeout to expire and then proceed to the next line. If you want to skip subsequent commands on failure, add set -e to the top of your Bash script to halt execution immediately.

Is this method safe for production environments?

It is safe for controlled environments where you trust the contents of the text file. Never use this method on untrusted data because eval can execute arbitrary shell commands, posing a significant security risk if the file is tampered with.