Bash - case 语句总是进入 default

Question

我正在编写一个 Bash 脚本来解析 CSV 文件(值由 ; 字符分隔)并提取一些参数。根据从文件中读取的当前参数，将特定字符串附加到变量。但是，case语句总是进入默认状态*)，我想不通为什么。

我读取 .csv 文件没有问题。已经这样做并显示了从文件中读取的参数的输出。一切都很完美。问题是 case 语句没有按预期处理。

因此，问题不在于读取 .csv 文件，而在于处理 case 语句中的参数。

这是我的代码:

while IFS=";" read -r arg
do
  case ${arg} in
    "valueX")
      var+="blabla"
      ;;
    "valueY")
      var+="blublu"
      ;;
    *)
      echo -e "Argument ${arg} not supported"
      exit 1
      ;;
  esac
done < filename

假设“valueX”是从文件中读取的当前参数。脚本总是以某种方式输出:

Argument "valueX" not supported

显然，从文件中读取的参数(此处:“valueX”)是正确的，但脚本不会进入相应的状态。相反，它总是进入默认状态，无论 ${arg} 持有什么值。

[编辑]我认为更笼统地问这个问题是个好主意，但结果却令人困惑。所以这是完整的 bash 脚本和 .csv 文件:

脚本:

#!/bin/bash

# style reset
STYLE_RESET='\e[0m'
# Red foreground color
FOREGROUND_RED='\e[31m'
# Green foreground color
FOREGROUND_GREEN='\e[32m'
# Blue foreground color
FOREGROUND_BLUE='\e[34m'
# Red background color
BACKGROUND_RED='\e[41m'
# Green background color
BACKGROUND_GREEN='\e[42m'
# Blue background color
BACKGROUND_BLUE='\e[44m'

SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"


usage()
{
    echo "ToDo"
    exit 1
}
# --------------------------------------- #
# --- Checking Command Line Arguments --- #
# --------------------------------------- #
# Supported command line arguments:
#   -h|--help
#   -a|--address    IP of SSH server for remote VMAF
#   -u|--user       User for SSH server login
#   -d|--doe        DoE worksheet exported as CSV UTF-8 file
PARAMS=""
while (( "$#" )); do
    case "$1" in
        -h|--help)
            usage
            shift
            ;;
        -u|--user)
            if [ -n "$2" ] && [ ${2:0:1} != "-" ]; then # Check length of argument and first character of argument != '-'
                SSH_USER=$2
                shift 2
            else
                echo "Error: Argument for $1 is missing" >&2
                exit 1
            fi
            ;;
        -a|--address)
            if [ -n "$2" ] && [ ${2:0:1} != "-" ]; then # Check length of argument and first character of argument != '-'
                SSH_IP=$2
                shift 2
            else
                echo "Error: Argument for $1 is missing" >&2
                exit 1
            fi
            ;;
        -d|--doe)
            if [ -n "$2" ] && [ ${2:0:1} != "-" ]; then # Check length of argument and first character of argument != '-'
                DOE_FILE=$2
                shift 2
            else
                echo "Error: Argument for $1 is missing" >&2
                exit 1
            fi
            ;;
        -*|--*=) # unsupported flags
            echo "Error: Unsupported flag $1" >&2
            exit 1
            ;;
        *) # DEFAULT
            PARAMS="${PARAMS} $1" # preserve positional arguments
            shift
            ;;
    esac
done
# set positional arguments in their proper place
eval set -- "${PARAMS}"


# ---------------------- #
# --- Processing DoE --- #
# ---------------------- #
echo -e "${BACKGROUND_BLUE}Processing DoE specified in file ${DOE_FILE}:${STYLE_RESET}"
echo -e "${BACKGROUND_BLUE}Configuring Video source for GStreamer pipeline...${STYLE_RESET}"
GSTPIPE_SRC="gst-launch-1.0 -e "
run=1
while IFS=";" read -r motion bitrate_in bitrate_out twopass iframe quantI quantP quantB mvbuffer cabac vbv
do
    echo -e "\n\n${BACKGROUND_BLUE}Setting #${run}:${STYLE_RESET}"
    echo -e "${BACKGROUND_BLUE}${motion} ${bitrate_in} ${bitrate_out} ${twopass} ${iframe} ${quantI} ${quantP} ${quantB} ${mvbuffer} ${cabac} ${vbv}${STYLE_RESET}"
    echo -e "\n${BACKGROUND_BLUE}Generating GStreamer pipelines...${STYLE_RESET}"

    case ${motion} in
        "low")
            GSTPIPE_SRC+="videotestsrc pattern=colors num-buffers=300 ! " # -> no motion content
            case ${bitrate_in} in   # -> bitrate of video source (width*height*framerate)
                "low") # -> 640x480
                    GSTPIPE_SRC+="'video/x-raw, width=(int)640, height=(int)480, framerate=(fraction)30/1, format=(string)I420' "
                    width=640
                    height=480
                    fps=30
                    ;;
                "high") # -> 3840x2160
                    GSTPIPE_SRC+="'video/x-raw, width=(int)3840, height=(int)2160, framerate=(fraction)30/1, format=(string)I420' "
                    width=3840
                    height=2160
                    fps=30
                    ;;
                *)
                    echo -e "\n\n${BACKGROUND_RED}Input bitrate ${bitrate_in} not supported${STYLE_RESET}"
                    echo -e "Use low, or high instead"
                    exit 1
                    ;;
            esac
            ;;
        "high")
            GSTPIPE_SRC+="filesrc location=${SCRIPT_DIR}/extensive.mp4 " # -> high motion content
            case ${bitrate_in} in   # -> bitrate of video source (width*height*framerate)
                "low") # -> 640x480
                    GSTPIPE_SRC+="blocksize=460800 ! " # blocksize=width*height*bytesPerPixel (I420->12bit->bytesPerPixel=1.5)
                    GSTPIPE_SRC+="'video/x-raw, width=(int)640, height=(int)480, framerate=(fraction)30/1, format=(string)I420' "
                    width=640
                    height=480
                    fps=30
                    ;;
                "high") # -> 3840x2160
                    GSTPIPE_SRC+="blocksize=12441600 ! " # blocksize=width*height*bytesPerPixel (I420->12bit->bytesPerPixel=1.5)
                    GSTPIPE_SRC+="'video/x-raw, width=(int)3840, height=(int)2160, framerate=(fraction)30/1, format=(string)I420' "
                    width=3840
                    height=2160
                    fps=30
                    ;;
                *)
                    echo -e "\n\n${BACKGROUND_RED}Input bitrate ${bitrate_in} not supported${STYLE_RESET}"
                    echo -e "Use low, or high instead"
                    exit 1
                    ;;
            esac
            ;;
        *)
            echo -e "${BACKGROUND_RED}Argument ${motion} for DoE factor 'motion' not supported${STYLE_RESET}"
            echo -e "Use low, or high instead"
            exit 1
            ;;
    esac

    GSTPIPE_ENC=$GSTPIPE_SRC
    GSTPIPE_REF=$GSTPIPE_SRC

    GSTPIPE_REF+="! y4menc ! filesink location=${SCRIPT_DIR}/reference${fps}fps_run${run}.y4m"

    GSTPIPE_ENC+="! nvvidconv ! 'video/x-raw(memory:NVMM)' ! nvv4l2h264enc "
    GSTPIPE_ENC+="bitrate=${bitrate_out} EnableTwopassCBR=${twopass} "
    case ${iframe} in
        "low")
            GSTPIPE_ENC+="iframeinterval=20 SliceIntraRefreshInterval=10 "
            ;;
        "high")
            GSTPIPE_ENC+="iframeinterval=120 SliceIntraRefreshInterval=60 "
            ;;
        *)
            echo -e "${BACKGROUND_RED}Argument ${motion} for DoE factor iframe is not supported${STYLE_RESET}"
            echo -e "Use low, or high instead"
            exit 1
            ;;
    esac
    # The range of B frames does not take effect if the number of B frames is 0. (https://docs.nvidia.com/jetson/l4t/index.html#page/Tegra%20Linux%20Driver%20Package%20Development%20Guide/accelerated_gstreamer.html#wwpID0E0YX0HA)
    GSTPIPE_ENC+="quant-i-frames=${quantI} quant-p-frames=${quantP} quant-b-frames=${quantB} num-b-frames=1 EnableMVBufferMeta=${mvbuffer} cabac-entropy-coding=${cabac} "
    GSTPIPE_ENC+="! nvv4l2decoder ! nvvidconv ! 'video/x-raw' ! y4menc ! filesink location=${SCRIPT_DIR}/distorted${fps}fps_run${run}.y4m"
    echo -e "${BACKGROUND_BLUE}Distorted Video:${STYLE_RESET}"
    echo -e "${FOREGROUND_BLUE}${GSTPIPE_ENC}${STYLE_RESET}"
    echo -e "${BACKGROUND_BLUE}Reference Video:${STYLE_RESET}"
    echo -e "${FOREGROUND_BLUE}${GSTPIPE_REF}${STYLE_RESET}"

    # --- Launching GStreamer pipelines (surpress detailed output) --- #
    echo -e "${BACKGROUND_BLUE}Launching GStreamer pipeline for encoded video (distorted):${STYLE_RESET}"
    eval "${GSTPIPE_ENC[@]}" #> /dev/null
    echo -e "${BACKGROUND_BLUE}Launching GStreamer pipeline for uncompressed video (reference):${STYLE_RESET}"
    eval "${GSTPIPE_REF[@]}" #> /dev/null

    # --- Create and Check Remote Directories --- #
    echo -e "\n${BACKGROUND_BLUE}Video transfer to remote machine:${STYLE_RESET}"
    SSH_DIR_ADD="v4l2h264/motion_${motion}/bitrate_${bitrate_in}/"
    SSH_DIR="/home/${SSH_USER}/metrics/${SSH_DIR_ADD}"  # Create variable holding path of directory for both:
                                                    #   1.) reference.y4m and distorted.y4m videos
                                                    #   2.) remote VMAF
    ssh ${SSH_USER}@${SSH_IP} "test -d ${SSH_DIR}" < /dev/null # see https://stackoverflow.com/questions/9393038/ssh-breaks-out-of-while-loop-in-bash
    if [ $? -ne 0 ]; then # Directory does not exist
        echo -e "${BACKGROUND_BLUE}Creating remote directory for run #${run}: ${SSH_DIR}...${STYLE_RESET}"
        ssh ${SSH_USER}@${SSH_IP} "mkdir -p ${SSH_DIR}" < /dev/null # see https://stackoverflow.com/questions/9393038/ssh-breaks-out-of-while-loop-in-bash
    else # Directory already exists
        echo -e "${BACKGROUND_BLUE}Remote directory ${SSH_DIR} already exists${STYLE_RESET}"
    fi

    # --- Transfer Video Files --- #
    echo -e "${BACKGROUND_BLUE}Transfering reference and distorted videos of run #${run}:${STYLE_RESET}"
    scp ${SCRIPT_DIR}/distorted${fps}fps_run${run}.y4m ${SSH_USER}@${SSH_IP}:${SSH_DIR} < /dev/null # see https://stackoverflow.com/questions/9393038/ssh-breaks-out-of-while-loop-in-bash
    scp ${SCRIPT_DIR}/reference${fps}fps_run${run}.y4m ${SSH_USER}@${SSH_IP}:${SSH_DIR} < /dev/null # see https://stackoverflow.com/questions/9393038/ssh-breaks-out-of-while-loop-in-bash

    # --- Run VMAF on Remote Machine --- #
    echo -e "\n${BACKGROUND_BLUE}Running VMAF metric for DoE run #${run} on remote machine...${STYLE_RESET}"
    ssh ${SSH_USER}@${SSH_IP} "vmaf -r ${SSH_DIR}/reference${fps}fps_run${run}.y4m -d ${SSH_DIR}/distorted${fps}fps_run${run}.y4m -w ${width} -h ${height} -p 420 -b 12 -o ${SSH_DIR}/log${fps}fps_run${run}.xml --threads 8" < /dev/null # see https://stackoverflow.com/questions/9393038/ssh-breaks-out-of-while-loop-in-bash
    echo -e "${BACKGROUND_BLUE}VMAF metric for DoE run #${run} finished.${STYLE_RESET}"

    # --- Remove Videos on Remote Machine (Laptop) --- #
    echo -e "\n${BACKGROUND_BLUE}Removing videos from remote machine${STYLE_RESET}"
    ssh ${SSH_USER}@${SSH_IP} "rm ${SSH_DIR}/distorted${fps}fps_run${run}.y4m ${SSH_DIR}/reference${fps}fps_run${run}.y4m" < /dev/null # see https://stackoverflow.com/questions/9393038/ssh-breaks-out-of-while-loop-in-bash

    # --- Remove videos on local machine (SPU) --- #
    echo -e "\n${BACKGROUND_BLUE}Removing videos from local machine${STYLE_RESET}"
    rm distorted${fps}fps_run${run}.y4m reference${fps}fps_run${run}.y4m

    ((run++))

done < <(cut -d ";" -f5,6,7,8,9,10,11,12,13,14,15,16 ${DOE_FILE} | tail -n +2) # read from the second line of the file (no header) and only read the columns specified with -f
((run--))

exit 0

.csv 文件:

"StdOrder";"RunOrder";"CenterPt";"Blocks";"motion";"bitrate_in";"bitrate_out";"twopass";"iframe";"quantI";"quantP";"quantB";"mvbuffer";"cabac"
1;1;1;1;"low";"low";200000;"false";"low";0;0;0;"true";"true"
6;2;1;1;"high";"low";80000000;"false";"low";51;0;51;"true";"false"
8;3;1;1;"high";"high";80000000;"false";"high";0;0;0;"false";"true"
2;4;1;1;"high";"low";200000;"false";"high";0;51;51;"false";"false"
3;5;1;1;"low";"high";200000;"false";"high";51;0;51;"false";"false"
7;6;1;1;"low";"high";80000000;"false";"low";0;51;51;"true";"false"
10;7;1;1;"high";"low";200000;"true";"high";51;0;0;"true";"false"
9;8;1;1;"low";"low";200000;"true";"low";51;51;51;"false";"true"
4;9;1;1;"high";"high";200000;"false";"low";51;51;0;"true";"true"
13;10;1;1;"low";"low";80000000;"true";"high";0;0;51;"true";"true"
5;11;1;1;"low";"low";80000000;"false";"high";51;51;0;"false";"true"
12;12;1;1;"high";"high";200000;"true";"low";0;0;51;"false";"true"
15;13;1;1;"low";"high";80000000;"true";"low";51;0;0;"false";"false"
14;14;1;1;"high";"low";80000000;"true";"low";0;51;0;"false";"false"
16;15;1;1;"high";"high";80000000;"true";"high";51;51;51;"true";"true"
11;16;1;1;"low";"high";200000;"true";"high";0;51;0;"true";"false"

Answer 1

Apparently, the argument (here: "valueX") read from the file is correct

由于您认为引号是参数的一部分是正确的，为了将它们与 case 模式匹配，您必须转义模式引号:

  case ${arg} in
    \"valueX\")

有趣的是，这似乎是一个 Bash ( documentation) 错误，正如上面所说的那样:

Each pattern undergoes tilde expansion, parameter expansion, command substitution, and arithmetic expansion.

它并没有说明该模式经历了引用删除。