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XK0-004 · Question #201

An administrator notices the HISTSIZE variable is 50, using the commands below: HISTSIZE=50 export HISTSIZE The administrator rechecks the HISTSIZE value using echo HISTSIZE but gets no value. Which o

The correct answer is A. printenv | grep $HISTSIZE. Using echo HISTSIZE without a dollar sign prints the literal string rather than the variable's value; printenv lists exported variables with their values and can be filtered to retrieve them.

Scripting, Containers and Automation

Question

An administrator notices the HISTSIZE variable is 50, using the commands below:

HISTSIZE=50 export HISTSIZE The administrator rechecks the HISTSIZE value using echo HISTSIZE but gets no value. Which of the following commands should the administrator use to retrieve its value?

Options

  • Aprintenv | grep $HISTSIZE
  • Becho HISTSIZE
  • Cprintf HISTSIZE
  • Dgrep $HISTSIZE

How the community answered

(40 responses)
  • A
    83% (33)
  • B
    3% (1)
  • C
    5% (2)
  • D
    10% (4)

Why each option

Using `echo HISTSIZE` without a dollar sign prints the literal string rather than the variable's value; `printenv` lists exported variables with their values and can be filtered to retrieve them.

Aprintenv | grep $HISTSIZECorrect

`printenv` outputs all currently exported environment variables in `NAME=value` format. Piping to `grep $HISTSIZE` causes the shell to expand the variable first (to 50), so the effective command is `grep 50`, which matches and displays the line `HISTSIZE=50` from `printenv` output. Because the variable was explicitly exported, it appears in `printenv`'s output, making this the only option that reliably retrieves the value.

Becho HISTSIZE

`echo HISTSIZE` prints the literal string 'HISTSIZE' because no `$` prefix is used to trigger variable expansion, which is the exact mistake the administrator already made.

Cprintf HISTSIZE

`printf HISTSIZE` also treats the argument as a literal format string with no variable expansion, printing 'HISTSIZE' rather than its value.

Dgrep $HISTSIZE

`grep $HISTSIZE` without a file argument or pipe source waits for standard input and never searches environment variables, so it will not return the variable's definition.

Concept tested: Retrieving exported shell environment variable values

Source: https://www.gnu.org/software/bash/manual/bash.html#index-printenv

Topics

#environment variables#HISTSIZE#printenv#bash shell

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