Unix tools for common dev tasks

This guide highlights essential Unix utilities and debugger commands for everyday development workflows. Use it to quickly reference powerful command-line tricks and streamline common tasks.

xargs

man page

# Find and archive PNG images
$ find Pictures/ -name "*.png" -type f -print0 | xargs -0 tar -cvzf png.tar

# Find and delete directories named Pictures
$ find Downloads -name "Pictures" -type d -print0 | xargs -0 /bin/rm -v -rf "{}"

ps

man page

# View all processes
$ ps axu
$ ps -A

# View all processes for a user
$ ps -u {USERNAME}

# View a process by PID
$ ps a -p {PID}

# Kill a process named some_name
$ ps aux | grep some_name | grep -v grep | awk '{print $2}' | xargs kill -9

# List all currently running processes
$ ps -ef

# List open file descriptors
$ ls -l /proc/pid/fd

# Show running JVM instances
$ ps -ef | grep java

# View a process using a custom output format
$ ps -L -o pid,tid,state,time,%cpu,%mem,start_time 10427

openssl

wiki page

basic guide

# Generate an RSA private key
$ openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out pkey.pem

# View the private key
$ openssl pkey -in pkey.pem -text

# Generate a public key from a private key
$ openssl rsa -pubout -in pkey.pem -outform PEM -out pubkey.pem

# View the public key
$ openssl rsa -pubin -in pubkey.pem -text

# View certificates (PEM or CRT file)
$ openssl x509 -in aaa_cert.pem -noout -text
$ openssl x509 -in ca.crt -noout -text

# Create a CA certificate from a private key
$ openssl req -new -x509 -sha256 -key pkey.pem -out ca.crt -days 3650

# Create a CSR for a certificate authority
$ openssl req -new -key client_private.key -out client_request.csr

# Issue a new certificate from a CSR
$ openssl x509 -req -in client_request.csr -CA ca.crt -CAkey ca_private.key -out client.crt -days 365 -sha256

nm

man page

# Show symbols
# List symbols from an object or executable file
$ nm -g -C --defined-only *.o
$ nm a.out | c++filt -t | less
$ nm -a a.out | c++filt

# List symbols in a library file
$ nm -gDC lib_name.so | grep --color symbol_name

Mac C/C++ Debugger

Tell LLDB where the source code is located. The debugger uses it for all matching references.

$ (lldb) settings set target.source-map /build/dir/path /my/local/source/path

List all shared libraries associated with the current target.

$ (lldb) image list

Find a specific shared library associated with the current target.

$ (lldb) image list libmylib.so

Check whether a shared library has debug symbols for a specific file.

1. Find the location of your LLVM toolchain.

Tip

Example: /home/serhii/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/linux-x86_64/bin

2. Find the location of the .so library you want to check.

Run the command and specify the file name you want to inspect.

Tip

Example: /home/serhii/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-dwarfdump /path/to/your/sharedlibrary/my.so | grep file_name_for_check.cpp

Set breakpoints:

$ (lldb) breakpoint set -n function_name
$ (lldb) breakpoint set -f file_name.cpp -l line_number

$ (lldb) breakpoint list

Symbol lookup:

$ (lldb) image lookup -vn symbol

Dump all threads:

$ (lldb) bt all

Log thread frames:

$ (lldb) thread backtrace

Inspect simple variables:

$ (lldb) p
$ (lldb) po

awk

man page

# Output only the first field from each line
$ cat test.txt | awk '{print $1}'

curl

man page

POST request:

$ curl -X POST --form "file=@1.txt" -v http://example.com

POST request with authorization:

$ curl -X POST -H "Authorization: Bearer <token>" http://example.com -v -d 'post_body'

Kerberos authentication:

$ curl -v -k --negotiate -u user_name:pass http://example.com

NTLM authentication:

$ curl -v -k --ntlm -u user_name:pass http://example.com

Download a file:

curl -o filename.txt https://reqbin.com/echo

Connect with proxy:

$ curl -x localhost:8888 -k http://example.com

ADB (Android debugging tool)

CPU usage:

adb shell dumpsys cpuinfo
adb shell "top -n 1"

Activity stack:

adb shell dumpsys activity top | grep --color -A 4 "ACTIVITY"

APK locations:

Internal storage: /data/app/app.package.name-t2tip43AexOplAoWlN1KCQ==/base.apk

System storage: /data/data/app.package.name

External storage: /Android/data/app.package.name

Unlock bootloader (Settings -> OEM unlocking -> ON):

adb reboot bootloader
fastboot oem lock
fastboot oem unlock
fastboot reboot

Install APK in workspace:

adb shell pm list users
adb install -r --user 18 internal-debug-work.apk

CPU ABI check:

adb shell getprop ro.product.cpu.abi

Sign APK:

/Library/Android/sdk/build-tools/30.0.0/apksigner sign --ks /Desktop/key AppKinetics-App-debug.apk

Uninstall a package:

adb uninstall <package-name>

List packages:

adb shell pm list packages

Current activity:

adb shell dumpsys window windows | grep -E 'mCurrentFocus|mFocusedApp'

Grant permissions:

adb shell pm grant [package name] [permission name]
adb shell pm grant uk.co.richyhbm.monochromatic android.permission.WRITE_SECURE_SETTINGS

Text input:

adb shell input text

Force-stop app:

adb shell am force-stop <PACKAGE>

Current API version:

adb shell getprop | grep ro.build.version

Launch activity:

adb shell am start -n yourpackagename/.activityname

Device rotation:

adb shell content insert --uri content://settings/system --bind name:s:user_rotation --bind value:i:0

Reboot device:

adb reboot

Rotation:

adb shell content insert --uri content://settings/system --bind name:s:accelerometer_rotation --bind value:i:0
adb shell content insert --uri content://settings/system --bind name:s:user_rotation --bind value:i:1
adb shell content insert --uri content://settings/system --bind name:s:user_rotation --bind value:i:0

Key event:

adb shell input keyevent 82

Enable apps from unknown sources:

adb shell settings put global verifier_verify_adb_installs 0

Uninstall app from work profile:

List users:

adb shell pm list users

Find app:

adb shell pm list packages --user 10 | grep "rim"

Remove work profile:

Settings -> Accounts -> Remove work profile

App verification:

adb shell settings put global verifier_verify_adb_installs 0

find

man page

Case insensitive search

$ find . -iname "main*" -type f

Search by creation time

$ find . -type f -mmin -10  # Find files created less than 10 minutes ago

$ find . -type f -mmin +1 -mmin -10  # Find files created more than 1 minute and less than 10 minutes ago

$ find . -type f -mtime -10  # Find files created less than 1 day ago

Search files by size

$ find . -size +5G  # Find files larger than 5 GB
$ find . -size +5M  # Find files larger than 5 MB
$ find . -size +5k  # Find files larger than 5 KB

Search files only in the current directory

$ find . -name "*.jpg" -type f -maxdepth 1

Modify file permissions using find command

$ find sample_dir/ -exec chown name1:name2 {} +
$ find sample_dir/ -type d -exec chown 775 {} +

Delete files using find command

$ find . -name "*.jpg" -type f -exec rm {} +

Search for permissions

$ find . -perm 775

Search for files ending with .java or .kt extension

$ find . -type f \( -name "*.java" -o -name "*.kt" \)

Find a file named “needle” and stop searching once found

$ find / -name needle -print -quit

Find all files without permission 777

$ find / -type f ! -perm 777

Find all empty directories

$ find . -type d -empty

$ find /tmp -type d -empty

GCC (C/C++ compiler)

optimization

Static vs dynamic libraries

Help

$ g++ --help

Measure compilation time

$ /usr/bin/time g++ test.cpp -std=c++17

Warning options

-ansi -pedantic -Wall -Wextra -Weffc++

Git

Git visual tool -> gitk

Git merge tool -> git mergetool

Git diff tool -> git difftool

Install p4merger

Install 2 p4merger

Detach (move) subdirectory into separate a Git repository

DELETE REMOTE BRANCH

git push origin --delete my_remote_branch

PATCH

git format-patch -1 9921ac0990fc1afc0eb871a15554840aa724f894 -o patches

SQUASH

git rebase -i HEAD~N

CONFIG GLOBAL VARIABLES

git config --global user.name ""
git config --global user.email ""
git config --list

GIT HELP

git help <verb>

GIT INITIALIZE EMPTY REPO

git init

TO STOP TRACK THE REPO JUST REMOVE .git DIRECTORY

rm -rf .git

ADD ALL CURRENTLY UNTRACHED OR CHANGED FILES TO STAGE AREA

git add -A
git add -A my_dir/ - add modifiesd and deleted files
git add --no-all my_dir/ - add only modified files
git add -u (updated) - not add untracked files
git add .

GREATE BRANCH

git branch <branch-name>
git checkout <branch-name>

REMOVE FILE FROM A STAGE AREA

git reset <file>
git reset

CLONE REPO

git clone <url> <where to clone>

VIEW REMOTE REPO INFO

git remote -v

VIEW LOCAL AND REMOTE BRANCHES

git branch -a

PUSH BRANCH TO REMOTE REPO

git push -u <remote-repo> <local-branch>

MERGE BRANCH INTO MASTER

git merge <branch-name>

git pull <remote-repo-name> <branch-name>
git push <remote-repo-name> <branch-name>

DELETE BRANCH LOCALY OR REMOTLY

git branch -d <branch-name>
git push origin --delete <branch-name>

SHOW FILES WHICH WAS MEANT TO COMMIT

git log --stat

CHERRY-PICK

git cherry-pick <hash>

RESET COMMIT

git reset --soft <hash>
git reset [mixed reset]
git reset --hard <hash>

GET RID OFF UNTRACKED FILES/DIRECTORIES

git clean -df

SHOW your commits in the order when you last reference them

git reflog

STASH CRETATE STASH

git stash save "message"
git stash push -m "message"

git stash list

git stash apply <id>
git stash pop

git stash drop <id>
git stash clear

REVERT COMMIT WITHOUT CHANGING HISTORY

git revert [git-hash-commit]

Revert changes

git checkout — <file_name>

Globbing

tutorial

Special charactes:

* - matches any charactes

? - macthes one character

[] - matches single or range of characters

! - not operator

Tip

Example of string patterns:

1. office*
2. office
3. *.txt
4. office?.*
5. office[A2].* (matches officeA. + any extenction or office2. + any extenction strings)
6. office[!2]* (does not matche office2 )
7. [a-z].txt
8. [0-9].txt

Gradle

1. Run test

./gradlew --console plain connectedAndroidTest -Pandroid.testInstrumentationRunnerArguments.class=com.example.class#test_example

2. App build & install tasks

./gradlew installDebug
./gradlew assembleDebug
./gradlew assembleRelease

With flags

./gradlew -PAPP_ABI=armeabi-v7a app:assembleDebug

3. Execute single build script

./gradlew -b /path/to/some_script.gradle someTask

4. Dependency Insight

./gradlew -q dependencyInsight --dependency artifactGroupName

5. Gradle dependencies check

./gradlew -q app:dependencies
./gradlew app:resolvableConfigurations

Grep

man page

Simple search in file

$ grep -inw "John Williams" note.txt

Search in current directory including all text files

$ grep -inw -C 2 "John Williams" ./*.txt

Search in curent directory and its subdirectories

$ grep -inwr -C 2 "John Williams" .

Show file names which contain a match

$ grep -ilwr -C 2 "John Williams" .

Show file names which contain a match with number of macthes

$ grep -icwr -C 2 "John Williams" .

Invert match show lines which DOEAN’T contain a match word

$ grep -ivwr "John Williams" .

Show lines 5 which contains a word ‘git’ in a history

history | grep -m 5 git

history | grep --max-count=5 git

Show only mathing word and don’t print full line

grep -wiro -C 2  "Tom" .

Search for a word in .txt files

grep -iwro --include=\*.txt "Tom"

Search for a word in .txt and .cpp files

grep -iwro --include=\*.{txt,cpp} "Tom"

Search for a word in .txt and .cpp files and exclude dir

grep -iwro --include=\*.{txt,cpp} --exclude-dir=build "Tom"

grep -iwro --include=\*.{txt,cpp} --exclude-dir={build, temp} "Tom"

Find a line which contian vivek or raj word (OR option)

grep -E 'vivek|raj' temp.txt

All the lines that contain both “Dev” and “Tech” in it (in the same order (AND option)

grep -E 'Dev.*Tech' employee.txt

Find only line which begging with vivek word

grep ^vivek /etc/passwd

Find only line which ending with vivek word

grep vivek$ /etc/passwd

hexdump

man page

View file in hex format

cat file.txt | hexdump -C

Java

Install certificates for Java keystore (JAVA 8)

sudo $JAVA_HOME/bin/keytool -import -alias root_CA1 -keystore $JAVA_HOME/jre/lib/security/cacerts -file $downloaded_cert_file
sudo $JAVA_HOME/bin/keytool -importcert -file <cert> -cacerts -keypass changeit -storepass changeit -noprompt -alias <alias>

Default password for keystore: changeit

Java 11/17

$ ./bin/keytool -importcert -file <cert> -cacerts -keypass changeit -storepass changeit -noprompt -alias <alias>

$ sudo ./bin/keytool -importcert -file ~/Downloads/Cert.crt -keypass changeit -storepass changeit -keystore ./lib/security/cacerts -alias root_CA1

Where is a random uniq name for this cert in the java cert storage

Generate JNI header file from java file

$ javac -h . ClassName.java

keytool (Android tool for working with keystore)

Get certificate signing hash from key store

$ keytool -list -v -keystore NAME_OF_KEYSTORE -alias KEY_ALIAS

javap

doc

Disassample a class file

$ javap -v -p -s -sysinfo -constants <file name>.class