bash

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 Go to latest Published: Oct 25, 2025 License: MIT Imports: 7 Imported by: 0

Documentation

Overview

Package bash provides utilities for executing bash commands and processing their output. It includes functionality for process management, system monitoring, and output formatting.

Index

Constants

This section is empty.

Variables

View Source 
var (
	// ErrInvalidCommand indicates that command is invalid.
	ErrInvalidCommand = errors.New("invalid command")

	// ErrEmptyPID indicates that a process lookup returned an empty process ID.
	ErrEmptyPID = errors.New("empty process id")

	// ErrNotRunning indicates that the requested process is not currently running.
	ErrNotRunning = errors.New("process is not running")

	// ErrBashExecuteFailed indicates that a bash command execution failed.
	ErrBashExecuteFailed = errors.New("bash execute failed")
)

Common error definitions used throughout the package.

Functions

func CPUPercentByPID 

func CPUPercentByPID(pid string) (string, error)

CPUPercentByPID retrieves the CPU usage percentage for a specific process. The percentage represents the process's total CPU utilization since its start.

Parameters:

  • pid: The process ID as a string (e.g., "1234"). Must be a valid running process.

Returns:

  • string: CPU usage percentage with "%" suffix (e.g., "25.5%") Returns zeroValue + "%" ("0.0%") if:
  • Process is not found
  • Process is using 0% CPU
  • Command fails
  • error: Error from command execution if ps command fails, nil if successful (even if process shows 0% usage)

Behavior:

  • Uses 'ps S -p PID -o pcpu=' command to get CPU percentage
  • The 'S' option includes child processes in calculation
  • Automatically trims whitespace and appends "%" symbol
  • Returns string formatted to one decimal place

Example: 

cpu, err := CPUPercentByPID("1234")
if err != nil {
    log.Printf("CPU check failed: %v", err)
}
fmt.Printf("CPU Usage: %s", cpu) // e.g. "75.3%"

Notes:

  • CPU percentage is relative to a single core (may exceed 100% on multicore systems)
  • Requires 'ps' command to be available in system PATH
  • For containerized processes, results may differ from host metrics
  • Values are snapshots, not averages over time
  • Consider using multiple samples for monitoring trending usage.

func Execute 

func Execute(name string, args ...string) (string, error)

Execute runs a system command and captures its output streams. It provides a convenient wrapper around exec.Command with integrated error handling.

Parameters:

  • name: The name/path of the command to execute (e.g. "ls", "/bin/bash")
  • args: Variadic arguments to pass to the command (e.g. "-l", "-a")

Returns:

  • string: The combined stdout output of the command
  • error: Returns ErrBashExecuteFailed if stderr contains output, or the original exec error if the command failed to run. Returns nil if execution was successful with empty stderr.

Behavior:

  • Captures both stdout and stderr streams separately
  • Considers any stderr output as an error condition
  • Preserves the command's exit status error if present
  • Trims no output - returned strings may contain trailing newlines

Example: 

output, err := Execute("ls", "-l", "/tmp")
if err != nil {
    // Handle error (either from stderr or command failure)
}
fmt.Println(output)

Notes:

  • For bash commands, consider using commandBash constant as name
  • Command output is not stripped of ANSI codes (use Strip() separately)
  • Not suitable for interactive commands requiring stdin.

func GetLargeFileList 

func GetLargeFileList(path, mask string, params ...int) (string, error)

GetLargeFileList finds large files with specific extension in given path Parameters:

  • path: directory to search
  • ext: file extension to match (e.g. ".log")
  • params: optional count parameter (default 20)

Returns list of files or error if command fails.

func GetUptimeByPID 

func GetUptimeByPID(pid string) (string, error)

GetUptimeByPID retrieves the elapsed time since a process started using its PID. It executes the 'ps' command to get the process's running duration in format [[DD-]HH:]MM:SS.

Parameters:

  • pid: The process ID as a string (e.g., "12345"). Must be a valid running process ID.

Returns:

  • string: The process uptime in format:
  • "MM:SS" for processes running <1 hour
  • "HH:MM:SS" for processes running <1 day
  • "DD-HH:MM:SS" for processes running multiple days
  • uptimeZeroValue ("00:00:00") if the process is not found
  • error: Returns:
  • Original error if 'ps' command execution fails
  • nil if successful (even if process not found)

Behavior:

  • Uses 'ps -o etime= -p PID' command to get process duration
  • Automatically trims whitespace and newlines from output
  • Returns zero value (not error) if process doesn't exist
  • Output format matches system 'ps' command behavior

Example: 

uptime, err := GetUptimeByPID("12345")
if err != nil {
    log.Printf("Failed to check uptime: %v", err)
}
fmt.Printf("Process running for: %s", uptime) // e.g. "01:23:45"

Notes:

  • Requires 'ps' command to be available in system PATH
  • Unlike other functions, returns zero value rather than error for missing process
  • For empty/zero uptime, check against uptimeZeroValue constant
  • Uptime resolution is seconds (no milliseconds).

func MemAvail 

func MemAvail() (string, error)

MemAvail retrieves the total available system memory in megabytes (MB). This represents the physical RAM available for new processes, excluding buffers/cache.

Returns:

  • string: Total available memory formatted with " MB" suffix (e.g., "8192 MB") Returns zeroValue + " MB" ("0.0 MB") if:
  • Command execution fails
  • Unable to parse memory information
  • error: Error from command execution if the bash command fails, nil if successful

Implementation Details:

  • Uses bash command pipeline: 1. `free` command to get memory statistics 2. `awk` extracts the total memory value (column 2 from second line) 3. Converts from kilobytes to megabytes (/1024) 4. Formats as integer (%.0f) for clean output
  • Automatically trims whitespace/newlines from output
  • Adds " MB" suffix to clarify units

Example: 

availMem, err := MemAvail()
if err != nil {
    log.Printf("Failed to get available memory: %v", err)
}
fmt.Printf("Available system memory: %s", availMem) // e.g. "16384 MB"

Notes:

  • Measures physical RAM, not including swap space
  • Values are in binary megabytes (MiB, 1024-based)
  • Requires GNU free and awk utilities
  • Represents system-wide available memory
  • For accurate container memory limits, check cgroup settings.

func MemPercentByPID 

func MemPercentByPID(pid string) (string, error)

MemPercentByPID retrieves the memory usage percentage for a specific process. The percentage represents the process's resident memory relative to total system memory.

Parameters:

  • pid: The process ID as a string (e.g., "5678"). Must be a valid running process.

Returns:

  • string: Memory usage percentage with "%" suffix (e.g., "4.2%") Returns zeroValue + "%" ("0.0%") if:
  • Process is not found
  • Process uses 0% memory
  • Command execution fails
  • error: Error from command execution if ps command fails, nil if successful (even if process shows 0% usage)

Behavior:

  • Uses 'ps S -p PID -o pmem=' command to get memory percentage
  • The 'S' option includes child processes in calculation
  • Automatically trims whitespace and appends "%" symbol
  • Returns string formatted to one decimal place

Example: 

mem, err := MemPercentByPID("5678")
if err != nil {
    log.Printf("Memory check failed: %v", err)
}
fmt.Printf("Memory Usage: %s", mem) // e.g. "2.8%"

Notes:

  • Percentage is relative to total physical memory (RAM)
  • Does not include shared memory or swap usage
  • Requires 'ps' command to be available in system PATH
  • Values represent current snapshot, not averages over time.

func MemUsed 

func MemUsed() (string, error)

MemUsed retrieves the total used system memory in megabytes (MB). It calculates the actively used memory excluding buffers/cache.

Returns:

  • string: Total used memory formatted with " MB" suffix (e.g., "2048 MB") Returns zeroValue + " MB" ("0.0 MB") if:
  • Command execution fails
  • Unable to parse memory information
  • error: Error from command execution if the bash command fails, nil if successful

Implementation Details:

  • Uses bash command pipeline: 1. `free` command to get memory statistics 2. `awk` extracts the used memory value (column 3 from second line) 3. Converts from kilobytes to megabytes (/1024) 4. Formats as integer (%.0f) to remove decimal places
  • Automatically trims whitespace/newlines from output
  • Adds " MB" suffix to clarify units

Example: 

usedMem, err := MemUsed()
if err != nil {
    log.Printf("Failed to get system memory: %v", err)
}
fmt.Printf("System memory used: %s", usedMem) // e.g. "3752 MB"

Notes:

  • Measures actual used memory excluding buffers/cache
  • Values are in binary megabytes (MiB, 1024-based)
  • Requires GNU free and awk utilities
  • Represents system-wide memory usage, not per-process
  • Consider using /proc/meminfo for more detailed breakdown.

func MemUsedByPID 

func MemUsedByPID(pid string) (string, error)

MemUsedByPID calculates the total resident memory usage of a process and its children in megabytes. It sums the RSS (Resident Set Size) memory of all process threads and converts to MB.

Parameters:

  • pid: The process ID as a string (e.g., "1234"). Must be a valid running process.

Returns:

  • string: Memory usage formatted with " MB" suffix (e.g., "24.5 MB") Returns zeroValue + " MB" ("0.0 MB") if:
  • Process is not found
  • Process uses no resident memory
  • Command execution fails
  • error: Error from command execution if the bash command fails, nil if successful (even if memory usage is 0)

Implementation Details:

  • Uses bash command pipeline: 1. `ps -ylp PID` lists all threads with memory info 2. `awk` sums the RSS (column 8) and converts to MB (/1024)
  • Automatically trims whitespace/newlines from output
  • Adds " MB" suffix to clarify units

Example: 

memUsage, err := MemUsedByPID("1234")
if err != nil {
    log.Printf("Memory check failed: %v", err)
}
fmt.Printf("Memory used: %s", memUsage) // e.g. "45.2 MB"

Notes:

  • Measures physical RAM usage (RSS), not virtual memory
  • Includes memory used by all process threads
  • Values are in binary megabytes (MiB, 1024-based)
  • Requires GNU ps and awk utilities.

func PidofByProcess 

func PidofByProcess(process string) (string, error)

PidofByProcess retrieves the process ID (PID) of a running process by its name. It uses the system's 'pidof' command to find the PID of the specified process.

Parameters:

  • process: Name of the process to look up (e.g., "nginx", "java"). Should match the exact executable name.

Returns:

  • string: The PID of the process as a string if found.
  • error: May return:
  • Original error from command execution if pidof fails
  • ErrEmptyPID if process is not running or pidof returns empty
  • Other system errors if command cannot be executed

Behavior:

  • Executes 'pidof <process>' command internally
  • Automatically trims trailing newline from output
  • Returns first PID if multiple instances are running (pidof behavior)
  • Does not validate if the process is actually running beyond PID existence

Example: 

pid, err := PidofByProcess("nginx")
if err != nil {
    if errors.Is(err, ErrEmptyPID) {
        fmt.Println("Nginx is not running")
    } else {
        log.Fatalf("Error checking nginx: %v", err)
    }
}
fmt.Printf("Nginx PID: %s\n", pid)

Notes:

  • Requires pidof command to be available in system PATH
  • For more advanced process lookups, see PidofByProcessAndParam
  • Returned PID string may need conversion to int for numeric operations
  • On systems with multiple process instances, consider using pgrep instead.

func PidofByProcessAndParam 

func PidofByProcessAndParam(process, param string) (string, error)

PidofByProcessAndParam finds a process ID by process name and matching parameter. It executes a command pipeline: pgrep -af <process> | grep <param> to locate the specific process instance containing the given parameter.

Parameters:

  • process: The name of the process to search for (e.g. "java", "nginx")
  • param: The parameter string to match in the process command line (e.g. "--config=myapp.conf", "servername")

Returns:

  • string: The PID of the matching process
  • error: ErrEmptyPID if process is found but PID is empty, ErrNotRunning if no matching process is found, or other errors from command execution

Example: 

pid, err := PidofByProcessAndParam("java", "-Dapp.name=myapp")
if err != nil {
    // handle error
}.

func Strip 

func Strip(str string) string

Strip removes all ANSI escape sequences and trailing newline characters from a string. This is useful for cleaning up colored terminal output or formatted text.

Parameters:

  • str: The input string potentially containing ANSI codes

Returns:

  • A cleaned string with all ANSI sequences and trailing newlines removed

Example: 

cleaned := Strip("\033[32mHello\033[0m\n") // Returns "Hello".

Types

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Source Files

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