Shell脚本在while循环中调用esscs.sh报错：找不到主类a

执行读取文件的Shell脚本时，调用esscs.sh返回错误：Error: Could not find or load main class a

有问题的脚本如下：

cd /u01/oracle/essbase/products/Essbase/EssbaseServer/bin/cli/
while read application; do
        if [[ $application = "" || $application = "#"* ]]
        then
                continue
        else
                ./esscs.sh login -user usr -password xxx -essbaseurl https://bla/essbase
                ./esscs.sh lcmexport -application $application
        fi
done < /tmp/exportLCM_applications.txt

而以下脚本可正常运行：

cd /u01/oracle/essbase/products/Essbase/EssbaseServer/bin/cli/
./esscs.sh login -user usr -password xxx -essbaseurl https://bla/essbase
./esscs.sh lcmexport -application hardcodedapp

esscs.sh是Oracle Essbase的命令行工具，内容如下：

#!/bin/sh

export ERR_MSG_JAVA_REQUIRED="Install JDK8 and set JAVA_HOME variable to JDK8 installed location"

if [ -z "$JAVA_HOME" ]
then
    echo
    echo $ERR_MSG_JAVA_REQUIRED
    echo
    exit 1
fi

export JAVA_VERSION=$("$JAVA_HOME/bin/java" -version 2>&1 | awk -F '"' '/version/ {print $2}')

if [[ "$JAVA_VERSION" < "1.8" ]]
then
    echo
    echo You are using older java version $JAVA_VERSION
    echo $ERR_MSG_JAVA_REQUIRED
    echo
    exit 1
fi

export SCRIPT_DIRECTORY=$(dirname "$(readlink -f "$0")")
cd "$SCRIPT_DIRECTORY"

export CLI_HOME=.
export REST_CLI_HOME=$CLI_HOME/lib

export CLASSPATH=.:$REST_CLI_HOME/ess_rest_cli.jar:$REST_CLI_HOME/ess_es_server.jar:$REST_CLI_HOME/ess_japi.jar:$REST_CLI_HOME/ess_svp.jar:$REST_CLI_HOME/commons-cli.jar:$REST_CLI_HOME/commons-io.jar:$REST_CLI_HOME/jersey-client.jar:$REST_CLI_HOME/javax.ws.rs-api.jar:$REST_CLI_HOME/jersey-common.jar:$REST_CLI_HOME/hk2-utils.jar:$REST_CLI_HOME/hk2-apijar:$REST_CLI_HOME/javax.inject.jar:$REST_CLI_HOME/hk2-locator.jar:$REST_CLI_HOME/hk2-api.jar:$REST_CLI_HOME/javax-annotation-javax-annotation-api.jar:$REST_CLI_HOME/jackson-annotations.jar:$REST_CLI_HOME/jackson-core.jar:$REST_CLI_HOME/jackson-databind.jar:$REST_CLI_HOME/jackson-mapper-asl-1.9.2.jar:$REST_CLI_HOME/ojdl.jar:$REST_CLI_HOME/jersey-guava.jar:$REST_CLI_HOME/cglib.jar:$REST_CLI_HOME/jackson-core-asl-1.9.2.jar:$JAVA_HOME/db/lib/derby.jar:$REST_CLI_HOME/ojdbc8.jar:$REST_CLI_HOME/ess-platform-common.jar:$REST_CLI_HOME/datasource-model.jar:$REST_CLI_HOME/excel-core.jar:$REST_CLI_HOME/lz4-java.jar:$REST_CLI_HOME/avatica-core.jar:$REST_CLI_HOME/calcite-core.jar:$REST_CLI_HOME/calcite-linq4j.jar:$REST_CLI_HOME/protobuf-java.jar:$REST_CLI_HOME/janino.jar:$REST_CLI_HOME/json-path.jar:$REST_CLI_HOME/checker-qual.jar:$REST_CLI_HOME/jts-core.jar:$REST_CLI_HOME/commons-compiler.jar:$REST_CLI_HOME/guava.jar:$REST_CLI_HOME/failureaccess.jar:$REST_CLI_HOME/slf4j-api.jar:$REST_CLI_HOME/slf4j-nop.jar:$REST_CLI_HOME/commons-lang3.jar:$REST_CLI_HOME/ons.jar:$REST_CLI_HOME/oraclepki.jar:$REST_CLI_HOME/orai18n.jar:$REST_CLI_HOME/osdt_core.jar:$REST_CLI_HOME/osdt_cert.jar:$REST_CLI_HOME/simplefan.jar:$REST_CLI_HOME/ucp.jar:$REST_CLI_HOME/xdb6.jar:$REST_CLI_HOME/esscatalog-model.jar

原因 #

核心问题是while read循环通过标准输入重定向读取文件时，标准输入被文件占用。esscs.sh调用的Java程序或脚本内部可能隐式尝试读取标准输入，导致read命令提前获取到非预期内容，使得$application变量被错误赋值，最终传递给esscs.sh的参数异常，触发找不到主类的错误。

另外，原脚本中$application未加引号，若应用名称包含空格或特殊字符，会导致参数拆分错误，进一步加剧问题。

解决办法 #

1. 隔离循环的输入来源 #

使用文件描述符重定向，将文件读取绑定到非标准输入的描述符（如3），避免占用esscs.sh需要的标准输入：

cd /u01/oracle/essbase/products/Essbase/EssbaseServer/bin/cli/
while read -u3 application; do
        if [[ $application = "" || $application = "#"* ]]
        then
                continue
        else
                ./esscs.sh login -user usr -password xxx -essbaseurl https://bla/essbase
                ./esscs.sh lcmexport -application "$application"
        fi
done 3< /tmp/exportLCM_applications.txt

2. 给变量添加引号 #

将$application改为"$application"，防止应用名称含特殊字符时出现参数拆分错误，提升脚本健壮性。

3. 优化登录逻辑（可选） #

原脚本每次循环都执行登录操作，而Essbase CLI的登录状态会保留在会话中，可将登录命令移到循环外，减少重复操作：

cd /u01/oracle/essbase/products/Essbase/EssbaseServer/bin/cli/
./esscs.sh login -user usr -password xxx -essbaseurl https://bla/essbase
while read -u3 application; do
        if [[ $application = "" || $application = "#"* ]]
        then
                continue
        else
                ./esscs.sh lcmexport -application "$application"
        fi
done 3< /tmp/exportLCM_applications.txt

内容的提问来源于stack exchange，提问作者sebroux