I have a for loop that takes a CIDR that contains an illegal character for file names ("/").
part of the command is to save the output with the name of the CIDR.
for i in $(more subnets.lst);do shodan download $i-shodan net:$i;done
the download argument is followed by the result of the more command, which are the CIDR (192.168.21.0/24).
is there a way in bash to rename a variable while the loop is running ?
I remember doing this years back in batch files by subtracting from the str length, but that won't help me as I just need to replace the "/" with a "-"(or any other compliant char.
You can do this with using bash Parameter Expansion:
$ echo $var
192.168.21.0/24
$ echo "${var//\//-}"
192.168.21.0-24
So in your command, just use "${i//\//-}" whenever needed without changing the original value of $i. If you want to set variable i to the new value:
i="${i//\//-}"
On a side note, use while loop to read lines from a file, not cat, more or brothers, like:
while IFS= read -r line; do ....; done
I worked it out for myself:
for i in $(more subnets-test);do shodan download $(echo $i | tr "/" "-") net:$i;done
Related
I'm trying to figure out how to use a variable containing an ANSI-C quoting string as an argument for a subsequent bash command.
The string in the variable itself is a list of files (can virtually be a list of anything).
For example, I have a file containing a list of other files, for example test.lst containing :
>$ cat test.lst
a.txt
b.txt
c.txt
I need to pass the file content as a single string so I'm doing :
test_str=$(cat test.lst)
then converts to ANSI-C quoting string:
test_str=${test_str#Q}
So at the end I have :
>$ test_str=$(cat test.lst)
>$ test_str=${test_str#Q}
>$ echo $test_str
$'a.txt\nb.txt\nc.txt'
which is what I'm looking for.
Then problem arises when I try to reuse this variable as a string list in another bash command.
For example direct use into a for loop :
>$ for str in $test_str; do echo $str; done
$'a.txt\nb.txt\nc.txt'
What I expect at this step is that it prints the same thing as the content of the original test.lst
I also tried expanding it back but it leaves leading $' and trailing '
>$ str=${test_str#E}
>$ echo $str
$'a.txt b.txt c.txt'
I also tried printf and some other stuffs to no avail. What is the correct way to use such ANSI-C quoting variable into a bash command ?
How about:
eval echo "${test_str}"
I believe that an ANSI-C quoted string is meant to be evaluated by bash command line parser.
In the first place, why do you need quoting? Just keep the data untouched stored as elements of an array:
mapfile -t filelist < test.lst
# iterate through the list
for file in "${filelist[#]}"; do printf '%s\n' "$file"; done
I have the output file day by day:
linux-202105200900-foo.direct.tar.gz
The date and time string, ex: 202105200900 will change every day.
I need to manually rename these files to
linux-202105200900x86-foo.direct.tar.gz
( insert a short string x86 after date/time )
any bash script can help to do this?
If you're always inserting the string "x86" at character #18 in the string, you may use that command:
var="linux-202105200900-foo.direct.tar.gz"
var2=${var:0:18}"x86"${var:18}
echo $var2
The 2nd line means: "assign to variable var2 the first 18 characters of var, followed by x86 followed by the rest of the variable var"
If you want to insert "x86" just before the last hyphen in the string, you may write it like this:
var="linux-202105200900-foo.direct.tar.gz"
var2=${var%-*}"x86-"${var##*-}
echo $var2
The 2nd line means: "assign to variable var2:
the content of the variable var after removing the shortest matching pattern "-*" at the end
the string "x86-"
the content of the variable var after removing the longest matching pattern "*-" at the beginning
In addition to the very good answer by #Jean-Loup Sabatier another, perhaps more general way would simply be to replace the second occurrence of '-' with x86- which you can do with sed. Let's say you have:
fname=linux-202105200900-foo.direct.tar.gz
You can update that with:
fname="$(sed 's/-/x86-/2' <<< "$fname")"
Which simply uses a command substitution with sed and a herestring to modify fname assigning the modified result back to fname.
Example Use/Output
$ fname=linux-202105200900-foo.direct.tar.gz
fname="$(sed 's/-/x86-/2' <<< "$fname")"
echo $fname
linux-202105200900x86-foo.direct.tar.gz
Do you need this?
❯ dat=$(date '+%Y%m%d%H%M%S'); echo ${dat}
20210520170336
❯ filename="linux-${dat}x86-foo.direct.tar.gz"; echo ${filename}
linux-20210520170336x86-foo.direct.tar.gz
I wanted to go as simple as possible, considering only the timestamp is going to change, this script should do it. Just run it inside the folder where files are located and you'll get all of them renamed with x86.
#!/bin/bash
for file in $(ls); do
replaced=$(echo $file | sed 's|-foo|x86-foo|g')
mv $file $replaced
done
This is my output
filip#filip-ThinkPad-T14-Gen-1:~/test$ ls
linux-202105200900-foo.direct.tar.gz linux-202105201000-foo.direct.tar.gz linux-202105201100-foo.direct.tar.gz
filip#filip-ThinkPad-T14-Gen-1:~/test$ ./../development/bash-utils/bulk-rename.sh
filip#filip-ThinkPad-T14-Gen-1:~/test$ ls
linux-202105200900x86-foo.direct.tar.gz linux-202105201000x86-foo.direct.tar.gz linux-202105201100x86-foo.direct.tar.gz
Simply iterate through all the files in current folder and pipeline result to sed to replace regex -foo with x86-foo, then rename file with mv command.
As David mentioned in comment, if you're worried that there could be multiple occurrences of -foo then you can just replace g as global to 1 as first occurrence and that's it!
There is also the rename utility (https://man7.org/linux/man-pages/man1/rename.1.html), you could use:
rename -v 0-foo.direct.tar.gz 0x86-foo.direct.tar.gz *
which results in
`linux-202105200900-foo.direct.tar.gz' -> `linux-202105200900x86-foo.direct.tar.gz'
`linux-202205200900-foo.direct.tar.gz' -> `linux-202205200900x86-foo.direct.tar.gz'
`linux-202305200900-foo.direct.tar.gz' -> `linux-202305200900x86-foo.direct.tar.gz'
In addition to the very good answer by #David C. Rankin, just adding it in a loop and renaming the files
# !/usr/bin/bash
for file in `ls linux* 2>/dev/null` # Extract all files starting with linux
do
echo $file
fname="$(sed 's/-/x86-/2' <<< "$file")"
mv "$file" "$fname" # Rename file
done
Output recieved :
linux-202105200900x86-foo.direct.tar.gz
I have a bash script which asks for two arguments with a space between them. Now I would like to automate filling out the prompt in the command line with reading from a text file. The text file contains a list with the argument combinations.
So something like this in the command line I think;
for line in 'cat text.file' ; do script.sh ; done
Can this be done? What am I missing/doing wrong?
Thanks for the help.
A while loop is probably what you need. Put the space separated strings in the file text.file :
cat text.file
bingo yankee
bravo delta
Then write the script in question like below.
#!/bin/bash
while read -r arg1 arg2
do
/path/to/your/script.sh "$arg1" "$arg2"
done<text.file
Don't use for to read files line by line
Try something like this:
#!/bin/bash
ARGS=
while IFS= read -r line; do
ARGS="${ARGS} ${line}"
done < ./text.file
script.sh "$ARGS"
This would add each line to a variable which then is used as the arguments of your script.
'cat text.file' is a string literal, $(cat text.file) would expand to output of command however cat is useless because bash can read file using redirection, also with quotes it will be treated as a single argument and without it will split at space tab and newlines.
Bash syntax to read a file line by line, but will be slow for big files
while IFS= read -r line; do ... "$line"; done < text.file
unsetting IFS for read command preserves leading spaces
-r option preserves \
another way, to read whole file is content=$(<file), note the < inside the command substitution. so a creative way to read a file to array, each element a non-empty line:
read_to_array () {
local oldsetf=${-//[^f]} oldifs=$IFS
set -f
IFS=$'\n' array_content=($(<"$1")) IFS=$oldifs
[[ $oldsetf ]]||set +f
}
read_to_array "file"
for element in "${array_content[#]}"; do ...; done
oldsetf used to store current set -f or set +f setting
oldifs used to store current IFS
IFS=$'\n' to split on newlines (multiple newlines will be treated as one)
set -f avoid glob expansion for example in case line contains single *
note () around $() to store the result of splitting to an array
If I were to create a solution determined by the literal of what you ask for (using a for loop and parsing lines from a file) I would use iterations determined by the number of lines in the file (if it isn't too large).
Assuming each line has two strings separated by a single space (to be used as positional parameters in your script:
file="$1"
f_count="$(wc -l < $file)"
for line in $(seq 1 $f_count)
do
script.sh $(head -n $line $file | tail -n1) && wait
done
You may have a much better time using sjsam's solution however.
I'd like to convert a list separated with '\n' in another one separated with space.
Ex:
Get a dictionary like ispell english dictionary. http://downloads.sourceforge.net/wordlist/ispell-enwl-3.1.20.zip
My initial idea was using a variable as accumulator:
a=""; cat american.0 | while read line; do a="$a $line"; done; echo $a
... but it results '\n' string!!!
Questions:
Why is it not working?
What is the correct way to do that?
Thanks.
The problem is that when you have a pipeline:
command_1 | command_2
each command is run in a separate subshell, with a separate copy of the parent environment. So any variables that the command creates, or any modifications it makes to existing variables, will not be perceived by the containing shell.
In your case, you don't really need the pipeline, because this:
cat filename | command
is equivalent, in every way that you need, to this:
command < filename
So you can write:
a=""; while read line; do a="$a $line"; done < american.0; echo $a
to avoid creating any subshells.
That said, according to this StackOverflow answer, you can't really rely on a shell variable being able to hold more than about 1–4KB of data, so you probably need to rethink your overall approach. Storing the entire word-list in a shell variable likely won't work, and even if it does, it likely won't work well.
Edited to add: To create a temporary file named /tmp/american.tmp that contains what the variable $a would have, you can write:
while IFS= read -r line; do
printf %s " $line"
done < american.0 > /tmp/american.tmp
If you want to replace '\n' with a space, you can simply use tr as follows:
a=$(tr '\n' ' ' < american.0)
I would like to copy the contents of a variable (here called var) into a file.
The name of the file is stored in another variable destfile.
I'm having problems doing this. Here's what I've tried:
cp $var $destfile
I've also tried the same thing with the dd command... Obviously the shell thought that $var was referring to a directory and so told me that the directory could not be found.
How do I get around this?
Use the echo command:
var="text to append";
destdir=/some/directory/path/filename
if [ -f "$destdir" ]
then
echo "$var" > "$destdir"
fi
The if tests that $destdir represents a file.
The > appends the text after truncating the file. If you only want to append the text in $var to the file existing contents, then use >> instead:
echo "$var" >> "$destdir"
The cp command is used for copying files (to files), not for writing text to a file.
echo has the problem that if var contains something like -e, it will be interpreted as a flag. Another option is printf, but printf "$var" > "$destdir" will expand any escaped characters in the variable, so if the variable contains backslashes the file contents won't match. However, because printf only interprets backslashes as escapes in the format string, you can use the %s format specifier to store the exact variable contents to the destination file:
printf "%s" "$var" > "$destdir"
None of the answers above work if your variable:
starts with -e
starts with -n
starts with -E
contains a \ followed by an n
should not have an extra newline appended after it
and so they cannot be relied upon for arbitrary string contents.
In bash, you can use "here strings" as:
cat <<< "$var" > "$destdir"
As noted in the comment by Ash below, #Trebawa's answer (formulated in the same room as mine!) using printf is a better approach than cat.
All of the above work, but also have to work around a problem (escapes and special characters) that doesn't need to occur in the first place: Special characters when the variable is expanded by the shell. Just don't do that (variable expansion) in the first place. Use the variable directly, without expansion.
Also, if your variable contains a secret and you want to copy that secret into a file, you might want to not have expansion in the command line as tracing/command echo of the shell commands might reveal the secret. Means, all answers which use $var in the command line may have a potential security risk by exposing the variable contents to tracing and logging of the shell.
For variables that are already exported, use this:
printenv var >file
That means, in case of the OP question:
printenv var >"$destfile"
Note: variable names are case sensitive.
Warning: It is not a good idea to export a variable just for the sake of printing it with printenv. If you have a non-exported script variable that contains a secret, exporting it will expose it to all future child processes (unless unexported, for example using export -n).
If I understood you right, you want to copy $var in a file (if it's a string).
echo $var > $destdir
When you say "copy the contents of a variable", does that variable contain a file name, or does it contain a name of a file?
I'm assuming by your question that $var contains the contents you want to copy into the file:
$ echo "$var" > "$destdir"
This will echo the value of $var into a file called $destdir. Note the quotes. Very important to have "$var" enclosed in quotes. Also for "$destdir" if there's a space in the name. To append it:
$ echo "$var" >> "$destdir"
you may need to edit a conf file in a build process:
echo "db-url-host=$POSTGRESQL_HOST" >> my-service.conf
You can test this solution with running before export POSTGRESQL_HOST="localhost"