Example for decoding a JWT Payload with your Shell (bash, zsh...)

readme.md

Setup

Add this to your .profile, .bashrc, .zshrc...

decode_base64_url() {
  local len=$((${#1} % 4))
  local result="$1"
  if [ $len -eq 2 ]; then result="$1"'=='
  elif [ $len -eq 3 ]; then result="$1"'=' 
  fi
  echo "$result" | tr '_-' '/+' | openssl enc -d -base64
}

decode_jwt(){
   decode_base64_url $(echo -n $2 | cut -d "." -f $1) | jq .
}

# Decode JWT header
alias jwth="decode_jwt 1"

# Decode JWT Payload
alias jwtp="decode_jwt 2"

Usage

jwtp eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWV9.TJVA95OrM7E2cBab30RMHrHDcEfxjoYZgeFONFh7HgQ

Output

{
  "sub": "1234567890",
  "name": "John Doe",
  "admin": true
}

Not as good as @vithalreddy's solution, but with minimal reliance on jq for the header and payload:

# Decode JWT header, payload and expiration time
alias jwth='cut -d "." -f 1 | tr "_-" "+/" | awk "{while (length(\$0) % 4) { \$0 = \$0 \"=\" } print}" | base64 -d | jq'
alias jwtp='cut -d "." -f 2 | tr "_-" "+/" | awk "{while (length(\$0) % 4) { \$0 = \$0 \"=\" } print}" | base64 -d | jq'
alias jwtexp='cut -d "." -f 2 | tr "_-" "+/" | awk "{while (length(\$0) % 4) { \$0 = \$0 \"=\" } print}" | base64 -d | jq -r ".exp" | xargs -I {} sh -c "echo UTC: \$(date -u -d @{}) && echo Local: \$(date -d @{})"'