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When working with process management in Linux systems, we often need to target specific instances of a running process based on their full command-line arguments. The standard pidof or pgrep commands will return all matching processes by name, which isn't sufficient when you need to target a particular instance with specific parameters.

Consider this common situation in process management:

657 ?        S      0:00 processname software
658 ?        S      0:00 processname demo
659 ?        S      0:00 processname test

Standard commands would return all three PIDs:

$ pidof processname
657 658 659

The pgrep command with the -f flag allows matching against the full command line:

$ pgrep -f "processname test"
659

For more complex scenarios, consider these patterns:

# Case insensitive matching
pgrep -f -i "processname TEST"

# Full regex pattern matching
pgrep -f "^processname test$"

# Combining with other utilities
pgrep -f "processname test" | xargs ps -fp

When using these techniques:

• The -f flag makes pgrep match against the entire command line
• Quotes are important to handle spaces in arguments
• For production scripts, always validate the output
• Consider using -l flag to list process names for verification

While less flexible, pidof can be combined with other tools:

pidof processname | xargs -n1 ps -p | grep "test" | awk '{print $1}'

However, the pgrep solution is generally more efficient and reliable.

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When managing processes on Linux systems, we often need to target specific instances among multiple processes sharing the same name but having different command-line arguments. The standard pidof and pgrep commands return all matching PIDs by default, which isn't always what we need.

Consider this typical process listing:

657 ?        S      0:00 processname software
658 ?        S      0:00 processname demo
659 ?        S      0:00 processname test

The standard approaches have these limitations:

pidof processname  # Returns 657 658 659
pgrep processname  # Returns 657 658 659

These commands don't distinguish between the different argument variations.

The most effective solution is to use pgrep's -f flag which matches against the full command line:

pgrep -f "processname test"  # Returns just 659

Here are some practical examples demonstrating the power of this approach:

# Find nginx worker processes with specific configurations
pgrep -f "nginx: worker process -c /etc/nginx/special.conf"

# Locate Python scripts with specific module imports
pgrep -f "python.*import analyzer"

# Identify Java processes running particular JAR files
pgrep -f "java.*myapp\.jar.*--profile=production"

For systems without pgrep or when needing more complex matching:

ps -ef | grep "processname test" | grep -v grep | awk '{print $2}'

To actually send a HUP signal to our target process:

pkill -HUP -f "processname test"

Or if you need the PID for other operations:

target_pid=$(pgrep -f "processname test")
kill -HUP $target_pid

When using these techniques:

• Be aware of special characters in your command patterns
• Consider quoting your search patterns to prevent shell interpretation
• Test your patterns with pgrep -a first to verify matches
• Remember that -f matches the full command line including arguments

While pgrep -f is convenient, it's slightly slower than basic pgrep as it must examine the full command line of each process. For performance-critical scripts, consider more specific matching patterns.