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--- marc:linux:bash_snippets [2022/05/17 16:52] – marcv
+++ marc:linux:bash_snippets [2023/02/16 14:23] (current) – [Download files based on URLs in a file] marcv
@@ Line 1: / Line 1: @@
 ====== Some useful bash snippets: ======
+:!: If you declare variables, use lower case names!
+===== Using math =====
+<code>
+expr 30 + 10           # 30 + 10
+expr 30 - 10           # 30 - 10
+expr 30 / 10           # 30 / 10
+expr 30 \* 4           # 30 x 4, needs escape!
+</code>
 ===== Checking if file exists: =====
@@ Line 11: / Line 22: @@
 </code>
-=== Ask for variable input: ===
+===== Checking if directory exists: =====
+<code>
+if [[ -d ~/.ssh/ ]]
+then
+        echo "directory .ssh exists"
+else
+        echo "directory .ssh does not exist"
+fi
+</code>
+===== Checking if variable equals 200 =====
+<code>
+num = 200
+if [[ $num -eq 200 ]]
+then
+        echo "$num equals 200"
+else
+        echo "$num does not equal 200"
+fi
+</code>
+===== Ask for variable input: =====
 <code>
 # Read Password
@@ Line 21: / Line 53: @@
 </code>
-=== Ecnrypting / Decrypting file: ===
+===== Ecnrypting / Decrypting file: =====
 A useful tool for encrypting/decrypting files is //ccrypt//. Using this you can make use of //git// containing things like SSH keys:
@@ Line 32: / Line 64: @@
 </code>
-=== Install a list of programs: ===
+===== Install a list of programs: =====
 <code>
 progs=(
@@ Line 50: / Line 82: @@
 </code>
-=== A simple menu (ssh): ===
+===== A simple menu (ssh): =====
 <code>
@@ Line 110: / Line 142: @@
 clear
 exit</code>
+===== Conditional while loop: =====
+<code>
+if [ ! -f /usr/bin/zsh ]
+then
+	while true; do
+		read -p "Would you like to install 'zsh'? (y/n) " yn
+		case $yn in
+			[Yy]* ) echo "OK, installing zsh...";
+			while read program; do
+				sudo apt install -y "$program"
+			done <zsh
+			break;;
+    	    [Nn]* ) echo "ZSH will not be installed"; break;;
+        	* ) echo "Please answer yes or no.";;
+    	esac
+	done
+fi</code>
+===== Replace all files in a directory with empty files with the same name =====
+<code>
+#!/bin/bash
+# Get the directory path
+echo "Enter the path to the directory: "
+read dir_path
+# Check if the directory exists
+if [ ! -d "$dir_path" ]; then
+  echo "Error: Directory does not exist."
+  exit 1
+fi
+# Replace all files in the directory with empty files
+for file in "$dir_path"/*; do
+  if [ -f "$file" ]; then
+    > "$file"
+  fi
+done
+echo "All files in the directory have been replaced with empty files."
+</code>
+===== Find SSH logins =====
+:!: This script assumes that you have the sshpass package installed on your system. You can install it with the following command: sudo apt-get install sshpass (for Ubuntu) or brew install http://macappstore.org/sshpass/ (for macOS).
+<code>
+#!/bin/bash
+servers_file="servers"
+users_file="users"
+passwords_file="passwords"
+logins_file="logins.txt"
+# Check if the input files exist
+if [ ! -f "$servers_file" ] || [ ! -f "$users_file" ] || [ ! -f "$passwords_file" ]; then
+  echo "Error: One or more of the input files do not exist."
+  exit 1
+fi
+# Read the servers, users, and passwords into arrays
+servers=($(cat "$servers_file"))
+users=($(cat "$users_file"))
+passwords=($(cat "$passwords_file"))
+# Loop through all combinations of servers, users, and passwords
+for server in "${servers[@]}"; do
+  for user in "${users[@]}"; do
+    for password in "${passwords[@]}"; do
+      # Try to ssh into the server with the current combination of user and password
+      ssh_output=$(sshpass -p "$password" ssh "$user"@"$server" -o StrictHostKeyChecking=no -o ConnectTimeout=3 2>&1)
+      # Check if the ssh login was successful
+      if [ "$?" -eq 0 ]; then
+        echo "Successful ssh login to $server using account $user and password $password"
+        echo "$server $user $password" >> "$logins_file"
+      else
+        echo "Failed ssh login to $server using account $user and password $password"
+      fi
+    done
+  done
+done
+</code>
+===== Remove duplicate and empty lines from file =====
+<code>
+#!/bin/bash
+# Remove duplicate lines from url.txt and save to temp file
+sort -u url.txt > temp.txt
+# Remove empty lines from temp file and save back to url.txt
+grep -v "^$" temp.txt > url.txt
+# Remove temp file
+rm temp.txt
+</code>
+===== Download files based on URLs in a file =====
+<code>
+#!/bin/bash
+# read list of URLs from file
+while read url; do
+  # download file using wget
+  wget "$url"
+done < url.txt
+</code>
+Do the same but check if file exists. If it does compare sizes and ask what to do.
+<code>#!/bin/bash
+# Read URLs from the url.txt file and download the files
+while read url; do
+    filename=$(basename "$url")
+    if [ -e "$filename" ]; then
+        local_size=$(wc -c <"$filename")
+        remote_size=$(curl -sI "$url" | awk '/Content-Length/ {sub("\r",""); print $2}')
+        if [ "$local_size" = "$remote_size" ]; then
+            echo "$filename already exists and has the same file size. Skipping download."
+            continue
+        else
+            read -p "A file with the name $filename already exists. Do you want to save the new file with a different name? (y/n) " response
+            if [ "$response" = "y" ]; then
+                read -p "Enter the new file name: " new_filename
+                curl -L -o "$new_filename" "$url"
+                echo "File saved as $new_filename."
+            else
+                echo "Skipping download of $filename."
+            fi
+        fi
+    else
+        curl -L -o "$filename" "$url"
+        echo "Downloaded $filename."
+    fi
+done < url.txt
+</code>