Bash – Check if filename exist from inline command

bash

I have a file named input.txt with this contents:

…
FILE "Edie – Realities.txt" TXT
…

And I want to read it, then strip filename path from line that starts with FILE, and check if it exists, so:

[ -f $(cat input.txt | grep FILE | grep -o "\".*\"") ] && echo "exist" || echo "does not exist"

but this outputs:

[: too many arguments  
does not exist

If I run:

echo $(cat input.txt | grep FILE | grep -o "\".*\"")

I get what I expected:

"Edie - Realities.txt"

So why is this, or how can I solve this problem?

Best Answer

$(...) is evidently passing "Edie, -, and Realities.txt" as separate arguments. You need to quote $(...) like any other $variable, and you probably want to remove the "s.

[ -f "$(cat input.txt | grep FILE | sed 's/^.*"\(.*\)".*$/\1/')" ] && echo "exist" || echo "does not exist"

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Bash – Check whether files in a file list exist in a certain directory

The best way to iterate over the lines in a file is using the read builtin in a while loop. This is what you are looking for:

while IFS= read -r f; do
    if [[ -e $2/$f ]]; then
        printf '%s exists in %s\n' "$f" "$2"
    else
        printf '%s is missing in %s\n' "$f" "$2"
        exit 1
    fi
done < "$1"

Bash File Test – File Existence Test Always True

When your variable is empty, your command becomes:

[ -e ]

In this case, you call [..] with one argument -e. String "-e" is not null, so test return true.

This behavior is defined by POSIX test:

In the following list, $1, $2, $3, and $4 represent the arguments presented to test:

0 arguments:

Exit false (1).

1 argument:

Exit true (0) if $1 is not null; otherwise, exit false.

....

To make it works, you must double quote your variable:

[ -e "$MYAPPPATH" ]

This works because -e with an argument that is an empty string is false.

Best Answer

Related Solutions

Bash – Check whether files in a file list exist in a certain directory

Bash File Test – File Existence Test Always True

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