Giving parameters to bash via command line

Question

I have a bash script in which I want to run a a bunch of files of different times. Instead of creating a lot of if statements or creating a lot of bash scripts I was thinking if there's a way to accept which files to run in bash via command line.


#!/bin/bash

#generating training data

i_hard=0
i_soft=0
i_neutral=0

for entry in /home/noor/popGen/sweeps/slim_script/final/*
do
    if [[ $entry == *"hard_FIXED"* ]]; then
        echo "It's there!"
        /home/stuff/build/./test $entry > /home/noor/popGen/sweeps/msOut/final/hard_$i_hard.txt
        i_hard=$((i_hard+1))
    fi

    if [[ $entry == *"soft_FIXED"* ]]; then
        echo "It's there!"
        /home/stuff/build/./test $entry > /home/noor/popGen/sweeps/msOut/final/soft_$i_soft.txt
        i_soft=$((i_soft+1))
    fi
    if [[ $entry == *"neutral"* ]]; then
        echo "It's there!"
        /home/stuff/build/./test $entry > /home/noor/popGen/sweeps/msOut/final/neutral_$i_neutral.txt
        i_neutral=$((i_neutral+1))
    fi
done

What I want to do is:


#!/bin/bash


i=0

for entry in /home/final/*
do
    if [[ $entry == *parameter* ]]; then
        echo "It's there!"
        /home/stuff/build/./slim $entry > /home/final/parameter_$i.txt
        i=$((i+1))
    fi
done

So I want 'parameter' is what I want to give through command line which can be hard_FIXED, hard_0, and so on. How can I achieve that?

Here read this

Mihir Luthra
– Mihir Luthra

2019-08-30 11:45:28 +00:00
Commented Aug 30, 2019 at 11:45 — Mihir Luthra
– Mihir Luthra, Commented Aug 30, 2019 at 11:45

Mihir Luthra · Accepted Answer · 2019-08-30 11:41:00Z

2

The Shell Script Parameters by default are assigned as:

$N

Here: N is Number starting from 0.

Also, $0 refers to script file itself or the Shell.

So, the parameters passed to Shell Script are available as:

$1, $2, $3 and so on.

For example:

./script.sh hard_FIXED

hard_FIXED will be available as $1.

So, inside the script you can capture them and use as needed.

edited Aug 30, 2019 at 11:41

Mihir Luthra

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answered Aug 30, 2019 at 11:35

Punit Narang

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3 Comments

Peter Over a year ago

And if I want to pass the path to directory it'll be the same way as well?

Punit Narang Over a year ago

Yes, it will be the same way.

chepner Over a year ago

$0 is not a positional parameter; it's a special parameter. N starts at 1.

Alex Martian · Accepted Answer · 2019-08-30 11:37:15Z

1

The first argument to bash from a command line can be found with the positional parameter $1, so if I got your intentions right:

#!/bin/bash

#generating training data

i_hard=0
i_soft=0
i_neutral=0

for entry in /home/noor/popGen/sweeps/slim_script/final/*
do
    if [[ $entry == $1 ]]; then
        echo "It's there!"
        /home/stuff/build/./test $entry > /home/noor/popGen/sweeps/msOut/final/hard_$i_hard.txt
        i_hard=$((i_hard+1))
    fi

    if [[ $entry == $1 ]]; then
        echo "It's there!"
        /home/stuff/build/./test $entry > /home/noor/popGen/sweeps/msOut/final/soft_$i_soft.txt
        i_soft=$((i_soft+1))
    fi
    if [[ $entry == $1 ]]; then
        echo "It's there!"
        /home/stuff/build/./test $entry > /home/noor/popGen/sweeps/msOut/final/neutral_$i_neutral.txt
        i_neutral=$((i_neutral+1))
    fi
done

answered Aug 30, 2019 at 11:37

Alex Martian

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2 Comments

Peter Over a year ago

And if I want to pass path to directory, it'll be the same way as $1 for example and say $1/./test then?

Mihir Luthra Over a year ago

@Peter, if you called your script like ./script.sh path/to/dir, $1 will contain path/to/dir. $1/./test would mean path/to/dir/./test which is equivalent to path/to/dir/test. Also read about quotes in bash, you will probably need them sooner or later.

Walter A · Accepted Answer · 2019-08-30 12:03:14Z

1

Look how the parameters are used here.

#!/bin/bash

# parameter 1 directory
# parameter 2 entry
# check number arguments
if (( $# != 2 )); then
   echo "Usage: $0 directory entry"
   exit 1
fi

# different way of testing, now check directory
test -d "$1" || { echo "$1 is not a directory"; exit 1; }

i=0

for entry in /home/final/*${2}*
do
   # No need for testing [[ $entry == *parameter* ]], this is part of the loop
   echo "${entry}: It's there!"
   /home/stuff/build/slim "${entry}" > /home/final/${2}_$i.txt
   # Alternative for i=$((i+1))
   ((i++))
done

answered Aug 30, 2019 at 12:03

Walter A

20.2k2 gold badges29 silver badges46 bronze badges

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