CODEWITHSUNDEEP
bashcommand-line
olala
olala

Reputation: 4436

bash: how to execute a line from a file?

I guess this is easy but I couldn't figure it out. Basically I have a command history file and I'd like to grep a line and execute it. How do I do it?

For example: in the file command.txt file, there is:

wc -l *txt| awk '{OFS="\t";print $2,$1}' > test.log

Suppose the above line is the last line, what I want to do is something like this

tail -1 command.txt | "execute"

I tried to use 

tail -1 command.txt | echo

but no luck.

Can someone tell me how to make it work?

Thanks!

Upvotes: 0

Views: 591

Answers (5)

push.up.hoyv
push.up.hoyv

Reputation: 25

if you are expecting to execute the line several times in this bash session, consider adding it to an alias:

alias aa="$(tail -1 command.txt)"

then you could use aa<CR> to execute the content from the line.

Upvotes: 0

John B
John B

Reputation: 3646

You can use eval.

eval "$(tail -n 1 ~/.bash_history)"

or if you want it to execute some other line:

while read -r; do
    if some condition; then
        eval "$REPLY"
    fi
done < ~/.bash_history

Upvotes: 1

chepner
chepner

Reputation: 530940

You can load an arbitrary file into your shell's history list with

history -r command.txt

at which point you can use all the normal history expansion commands to find the command you wish to execute. For example, after executing the above command, the last line in the file would be available to run with

!!

Upvotes: 4

Reinstate Monica Please
Reinstate Monica Please

Reputation: 11593

Just use command substitution 

bash -c "$(tail -1 command.txt)"

Upvotes: 3

Eric Platon
Eric Platon

Reputation: 10122

Something like that?

echo "ls -l" | xargs sh -c

This answer addresses just the execution part. It assumes you have a method to extract the line you want from the file, perhaps a loop on each line. Each line of the file would be the argument for echo.

Upvotes: 1

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