A user keeps personal scripts in ~/bin. One of them is called grep, and the user wants their own version to be found before /usr/bin/grep, while every other command in the standard directories stays findable by name. Which line, added to a shell startup file, achieves that?
LPIC-1 Exam 102-500, objective 105. Shells and shell scripting medium
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How these questions are written — where each question comes from, what the verification ledger records, and what happens when one is found wrong.
The options
Correct export PATH="$HOME/bin:$PATH"
Correct. The search path is scanned left to right and the first match wins, so putting $HOME/bin ahead of the previous value makes the personal script shadow /usr/bin/grep.
Not correct export PATH="$PATH:$HOME/bin"
Wrong for this goal. This appends the directory, so /usr/bin is still reached first and the system grep continues to win. It is the safer form in general, but it does not do what was asked.
Not correct export PATH="$HOME/bin"
Wrong, and it breaks the shell. This replaces the entire search path, so ls, grep and every other command in /usr/bin become unfindable by name.
Not correct set PATH=$HOME/bin:$PATH
Wrong. That is C shell syntax. In bash, set with arguments assigns the positional parameters, so this leaves PATH untouched and merely sets $1 to the literal string.
Why
PATH is a colon-separated list searched in order, and the shell executes the first executable it finds, which is why position rather than membership decides who wins. Referring to $PATH inside the new value is what preserves the directories inherited from /etc/profile and the login process; omitting it discards them. Prepending a user-writable directory is deliberately shadowing system commands, so most sites append instead.
Where this comes from
- Cited
- manual page bash(1)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 105 and space the ones you get wrong.
More questions on this objective
- A user logs in at a text console, and bash starts as an interactive login shell. Which file in that user's home directory is read by bash itself as part of login startup? machine-checked
- You are already logged in to a graphical desktop and open a new terminal window, so bash starts as an interactive shell that is not a login shell. Which per-user file does bash read in that case? machine-checked
- An executable script contains only the line `export EDITOR=vim`. After running it as `./setenv.sh`, `echo $EDITOR` in the calling shell prints nothing. What explains this? machine-checked
- In bash, what is the effect of `export MYVAR`? machine-checked
- At a bash prompt you run `alias ll='ls -l'` and it works for the rest of that session, but a terminal window opened afterwards does not recognise `ll`. Which statement explains this and gives the standard remedy? machine-checked
- A command finishes and the shell reports an exit status of 0. What does that mean, and which parameter reports it? machine-checked