for i in a b c d

mackowiakp · 05-27-2023, 11:50 AM

I have in a file called "files" a listing of directories named - let's say - a, b, c, d, e, f etc. Each name is one line.
I would like to write a script in bash that will perform the following functions:

Code:

#!/bin/bash

ls -d -1 */|sed 's/\///' > files

for i in a c g
do
  # do something with $i
done

for i in <all others>
do
  # do something with any else $i
done

Can someone give me a hint how to do that?

teckk · 05-27-2023, 02:22 PM

Example:
Do something with lines 3 and 5
Something else with line 7
Something else with the rest.

Code:

n=1
while read line; do 
    if [ $n -eq 3 ] || [ $n -eq 5 ]; then
        echo "Do process A with line:"$n" "$line""
    elif [ $n -eq 7 ]; then
        echo "Do process B with line:"$n" "$line""
    else
        echo "Do process C with line:"$n" "$line""
    fi
    n=$((n + 1))
done < files

teckk · 05-27-2023, 02:50 PM

Or slice up an array

Code:

lines=($(cat files))

#First line
echo "${lines[0]}"

#Line 3-5
echo "${lines[@]:2:3}"

#Last 3
echo ${lines[@]: -3}

#2nd from last
echo ${lines[-2]}

Etc.

mackowiakp · 05-27-2023, 07:45 PM

Quote:

Do something with lines 3 and 5
Something else with line 7
Something else with the rest.

Its OK if You know numbers of the lines.
My problem is that I only know the subdirs names.
I have to do one thing with subdirs whose name does not change and another with other directories, which can be a different number and different names each time.

rkelsen · 05-27-2023, 09:23 PM

Is this a homework question?

Code:

#!/bin/bash

ls -d -1 */|sed 's/\///' > files

for i in `cat files` 
do 
    if [ $i = "a" ] || [ $i = "c" ] || [ $i = "g" ]; then
        echo "Hey I found $i"; else
        echo "You can ignore $i" 
    fi
done

Does that help?

mackowiakp · 05-28-2023, 12:56 AM

Quote:

Is this a homework question?

No ;-) But many thanks!

MadeInGermany · 05-28-2023, 03:22 AM

$( ) and ` ` produce an argument list that is split at whitespace including embedded spaces, and also by default do "filename generation".
A while-read loop can safely read lines from a text file:

Code:

while IFS= read -r fn
do
  case "$fn" in
  ( "a" | "c" | "g" )
    echo do something with "$fn"
  ;;
  ( * )
    echo do someth else with "$fn"
  ;;
  esac
done < file

pan64 · 05-28-2023, 10:44 AM

how do you know a directory belongs to the first group (or the second)?

mackowiakp · 05-28-2023, 05:32 PM

Quote:

how do you know a directory belongs to the first group (or the second)?

I know from this that the names of the first group of directories do not change and are called e.g. a, c, g etc.
The rest of the directories can take different names.

pan64 · 05-30-2023, 12:33 AM

Quote:

Originally Posted by mackowiakp

I know from this that the names of the first group of directories do not change and are called e.g. a, c, g etc.
The rest of the directories can take different names.

Ok, so you have some reserved names. I would make a list for them, an associative array like this:

Code:

R_DIRS[a]=1
R_DIRS[c]=1
....
for i in "${R_DIRS[@]}"
   do something with the reserved names
done
for i in <all dirs>
    [[ "${R_DIRS[$i]:-0}" -eq 1 ]] && continue
    do something with the others
done

MadeInGermany · 05-30-2023, 03:53 AM

The associative array with index-only:

Code:

R_DIRS["a"]=
R_DIRS["c"]=
....
for d in "${!R_DIRS[@]}"
do
   echo do something with "$d"
done
for d in <all dirs>
do
    [[ ${R_DIRS[$d]+exist} ]] && continue
    echo something else with "$d"
done

bash 4.2+ supports

Code:

    [[ -v R_DIRS[$d] ]] && continue

MadeInGermany · 05-30-2023, 04:31 AM

Another idea: extglob
(untested)

Code:

#!/bin/bash
shopt -s extglob nullglob
dirpat="a|c|g"
for d in @($dirpat)/
do
  echo do sth with "$d"
done
for d in !($dirpat)/
do
  echo do sth else with "$d"
done