Bagaimana untuk Melaksanakan Perintah Berbilang Baris dalam Baris Perintah Satu Baris?

Executing Multi-Line Commands in a One-Line Command Line

When using Python's -c option to execute a one-line loop, importing a module before the loop can result in a syntax error. This issue arises because the command line treats the entire command as a single line of code.

To overcome this limitation, there are several approaches:

• Using Echo:

  <code class="bash">echo -e "import sys\nfor r in range(10): print 'rob'" | python</code>

  This command uses echo to insert line breaks into the command string, which Python then interprets as multiple lines.

• Using Exec:

  <code class="bash">python -c "exec(\"import sys\nfor r in range(10): print 'rob'\")"</code>

  This approach uses the exec function to dynamically execute a string as Python code.

• Using Subshells:

  <code class="bash">(echo "import sys" ; echo "for r in range(10): print 'rob'") | python</code>

  This command splits the command into multiple lines using subshells. Each line is then executed independently.

• Using Crast's Answer:

  <code class="bash">python3 -c "import sys ; for r in range(10) : print('rob')"</code>

  This approach adds a semicolon before the for loop to indicate that the import statement is a separate command.

• Using SilentGhost's Answer:

  <code class="bash">python3 -c "import sys ; x = [print('rob') for r in range(10)][0]"</code>

  This approach uses Python's list comprehension syntax to execute the loop and assign the first result to x.

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