將命令輸出轉換爲bash中的變量和修剪變量？

Question

我有我想從一個bash腳本是運行一個命令：

ec2-create-volume -s 5 -z us-west-1c 

我願把這個命令的輸出到一個變量是：

VOLUME vol-091b6065 5  us-west-1c creating 2011-06-02T23:13:02+0000 

我會喜歡把輸出變成一個變量，並把變量全部從變量中刪除，所以我只剩下一個變量，它會讀取「vol-091b6065」

Answer 1

簡單而直接：

ec2-create-volume -s 5 -z us-west-1c | cut -f2 

，或者直接將其分配給一個變量：

myvolid=$(ec2-create-volume -s 5 -z us-west-1c | cut -f2) 

我用使用aws_utils.sh腳本喜歡這個，也許你可以從中收集一些提示：

#!/bin/bash 
#set -o xtrace 

#aws_numinstances=1 
#aws_amiid=ami-1515f67c 
#aws_delay=4 
#aws_keyname=gsg-keypair 

if [ -z "$aws_azone" ] 
then 
    aws_azone=us-east-1b 
    echo selected default zone of $aws_azone 
else 
    echo using configured zone of $aws_azone 
fi 

# handy in case we get interactively 'sourced' from a shell; make the temp(?) env var stick 
export DEBUG 
export VERBOSE 

# unalias aws_debug 

function aws_croak() 
{ 
    if [ ! -z "$VERBOSE" ]; then echo "$@"; fi 
} 

function aws_command() 
{ 
    if [ 1 != $# ]; then echo "WARNING: Quotes recommended (often required) on aws_command: '""$@""'" > /dev/stderr; fi 

    if [ ! -z $VERBOSE ]; then echo AWS: "$@" > /dev/stderr; fi 
    eval "$@" 
} 

function aws_debug() 
{ 
    if [ -z "$DEBUG" ] 
    then 
     aws_command "$@" 
    else 
     eval "echo AWS_DEBUG: '$@'" > /dev/stderr 
    fi 
} 

function aws_stubbing() 
{ 
    if [ -z "$DEBUG" ] 
    then 
     true 
    else 
     false 
    fi 
} 

function aws_launch() 
{ 
    aws_debug "ec2-run-instances $aws_amiid -k $aws_keyname -n $aws_numinstances -z $aws_azone|tee runlog|grep $aws_amiid|cut -f2" 
    aws_stubbing || echo "i-00000000" 
} 

function aws_all_inactive_volumes() 
{ 
    aws_command "ec2-describe-volumes|grep available|cut -f2" 
} 

# find any snapshots that don't have corresponding volumes (a) available or 
# already attached to our instance (b) in the correct availability zone 
function aws_unlinked_snaps() 
{ 
    #           egrep -w "available|$aws_instanceid" | 
    sort <(aws_command "ec2-describe-volumes | grep -v delet     | grep $aws_azone | cut -f4"; 
      aws_command "ec2-describe-snapshots | cut -f2") | 
     uniq -u 
} 

function aws_instance_hostname() 
{ 
    aws_debug "ec2-describe-instances | grep $aws_azone | grep $aws_instanceid | cut -f4" 
    aws_stubbing || echo "dumnmy-ec2.sehe.nl" 
} 

function aws_instance_status() 
{ 
    aws_debug "ec2-describe-instances | grep $aws_azone | grep $aws_instanceid | cut -f6" 
    aws_stubbing || echo "running" 
} 

# select all volumes and attach them to our instance; these could fail if the 
# volumes have already been attached to the instance 
function aws_attach_all_available_volumes() 
{ 
    dev_index=0 
    for letter in g h i j k l m n o p q r s t u v w x y z; do devlist[${#devlist[@]}]=/dev/sd$letter; done 

    for volid in $(aws_command "ec2-describe-volumes | egrep -w available\|$aws_instanceid | grep $aws_azone | cut -f2") 
    do 
     devname=${devlist[$dev_index]} 
     dev_index=$(($dev_index+1)) 
     aws_debug "ec2-attach-volume $volid -i $aws_instanceid -d $devname"& 
    done 
} 

# detach all volumes from our instance 
function aws_detach_all_volumes() 
{ 
    for volid in $(aws_command "ec2-describe-volumes | grep -w attached | grep $aws_instanceid | cut -f2") 
    do 
     aws_debug "ec2-detach-volume $volid -i $aws_instanceid"& 
    done 
} 

# awaits all volume operations in our zone (attaching|detaching|creating) 
# TODO: 
# this might be improved by filtering the attaching/detaching operations to 
# our aws_instanceid only 
function aws_wait_volume_operations() 
{ 
    while aws_stubbing 
    do 
     # funky quoting construct ahead, sry; 
     # the tack-on 'true' is to avoid aborting if 'set -e' is in effect 
     response="$(aws_command "ec2-describe-volumes | grep $aws_azone | egrep -w 'attaching|busy|detaching|creating'; true")" 
     # aws_croak "response: '$response'" 
     if [ -z "$response" ] 
     then 
      break 
     else 
      aws_croak '(volumes not ready...)' 
      sleep $aws_delay 
     fi 
    done 
} 

aws_croak "(aws_utils.sh loaded)" 

Answer 2

如果名字總是以vol-開頭，那麼你可以使用grep：

ec2-create-volume -s 5 -z us-west-1c | grep -o "vol-[^ ]*" 

Answer 3

你可以做到這一點：

myvar=$(ec2-create-volume -s 5 -z us-west-1c | awk '{print $2}') 

下面的記錄表明，在行動：

pax$ myvar=$(echo 'VOLUME vol-091b6065 blah blah' | awk '{print $2}') 

pax$ echo $myvar 
vol-091b6065