Bash：尝试制作一个“sed-replace”函数，对任意字符输入（扩展、替换等）具有鲁棒性

Question 1

这是脚本的修改版本，仅适用于第一个测试用例：

#!/usr/bin/env bash

inFile='/tmp/makefileTest'

sedReplace(){
    charsFoundFromGrep="$(grep -in "$1" "$inFile" | wc -c)"

    if [ "$3" == "$charsFoundFromGrep" ]; then
        # 1. The single quotes inside double quotes are threat as regular characters
        # 2. During the assignment, the variables $1, $2 and $inFile will be expanded
        # 3. The variable $execLine will have the following value:
        #    sed -i 's/CFLAGS += -Wunused # this is a comment/CFLAGS += -Wall # here I changed something/g' '/tmp/makefileTest'
        execLine="sed -i 's/$1/$2/g' '$inFile'"

        # We need 'eval' to convert the variable to a command in this case,
        # because the value of the variable contains spaces, quotes, slashes, etc.
        eval "$execLine"
    else
        echo "ERROR: Unhandled custom makefile modification (expected: $1)), please fix..."
        exit 1
    fi
}

sedReplace 'CFLAGS += -Wunused # this is a comment' 'CFLAGS += -Wall # here I changed something' '41'

上面的例子中使用了命令eval，最近我们在最后一部分讨论了它的用法、优缺点这个答案eval以及相关评论。如果可能的话，最好避免使用，因此我的下一个建议是：

#!/usr/bin/env bash

sedReplace(){
    # 1. Note we do not need to store the output of the command substitution $()
    #    into a variable in order to use it within a test condition.
    # 2. Here is used the bash's double square brackets test [[, so
    #    we do not need to quote the variable before the condition.
    #    If the statement after the condition is not quoted the (expanded) value
    #    will be threat as regexp. Currently it is treated as string.
    if [[ $3 == "$(grep -in "$1" "$inFile" | wc -c)" ]]
    then
        # 1. Note the double quotes here.
        # 2. The sed's /g flag is removed, because, IMO, we don't need it in this case at all.
        sed -i "s/$1/$2/" "$inFile"

    else
        echo "ERROR: Unhandled custom makefile modification (expected: $1)), please fix..."
        exit 1
    fi
}

# here are used double quotes in case the value comes from a variable in the further versions
inFile="/tmp/makefileTest"

sedReplace 'CFLAGS += -Wunused # this is a comment' 'CFLAGS += -Wall # here I changed something' '41'

上述示例仍然仅适用于第一个测试用例。对于其余测试用例，我们需要使用grep -F固定字符串 (参考)。此外，在使用之前，我们需要替换搜索字符串/模式中的某些字符sed（可能有更优雅的解决方案，但我找不到）。我们需要做的第三件事是将sed的分隔符从更改/为字符串中未使用的任何字符 - 在下面的示例中使用的是:。

此外，我还将输入文件的名称作为位置参数，并将位置参数分配给局部变量以便于阅读。

这是最终的解决方案（取消注释-i以进行实际更改）：

#!/usr/bin/env bash
sedReplace() {
    local the_searched_string="$1" the_replacement="$2" the_lenght="$3" the_file="$4"

    if [[ $the_lenght == "$(grep -inF "$the_searched_string" "$the_file" | wc -c)" ]]
    then
        the_searched_string="$(sed -r 's/(\^|\$|\\)/./g' <<< "$the_searched_string")" # replace some special characters within the searched string by any char '.'
        sed "s:$the_searched_string:$the_replacement:" "$the_file" #-i
    else
        echo "ERROR: Unhandled custom makefile modification (expected: ${the_searched_string})..."
        exit 1
    fi
}

inFile="/tmp/makefileTest" 

# Test all cases:
echo -e '\n\n# --- Test case 1 -----'
the_string='CFLAGS += -Wunused # this is a comment'
sedReplace "$the_string" \
           'CFLAGS += -Wall # something is changed' \
           "$(wc -c <<< '2:'"$the_string")" \
           "$inFile"
echo -e '\n\n# --- Test case 2 -----'
the_string='cp $(OBJ_DIR)/$(EXE_NAME) /tmp/somewhere'
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(wc -c <<< '5:'"$the_string")" \
            "$inFile"
echo -e '\n\n# --- Test case 3 -----'
the_string='cd $(SOME_UTIL_BIN); ./somecommand $(BUILD_DIRECTORY_PATH)/$(OBJ_DIR)/\$\^'
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(wc -c <<< '8:'"$the_string")" \
           "$inFile"

也许，根据您的需要，您可以使用sha256sum（或其他校验和工具）来 wc -c进行更严格的线路检查：

#!/usr/bin/env bash
sedReplace() {
    local the_searched_string="$1" the_replacement="$2" the_lenght="$3" the_file="$4"

    if [[ $the_lenght == "$(grep -inF "$the_searched_string" "$the_file" | sha256sum)" ]]
    then
        the_searched_string="$(sed -r 's/(\^|\$|\\)/./g' <<< "$the_searched_string")" # replace some special characters within the searched string by any char '.'
        sed "s:$the_searched_string:$the_replacement:" "$the_file" #-i
    else
        echo "ERROR: Unhandled custom makefile modification (expected: ${the_searched_string})..."
        exit 1
    fi
}

inFile="/tmp/makefileTest"

# Test all cases:
echo -e '\n\n# --- Test case 1 -----'
the_string='CFLAGS += -Wunused # this is a comment'; the_line='2'
sedReplace "$the_string" \
           'CFLAGS += -Wall # something is changed' \
           "$(sha256sum <<< "${the_line}:${the_string}")" \
           "$inFile"
echo -e '\n\n# --- Test case 2 -----'
the_string='cp $(OBJ_DIR)/$(EXE_NAME) /tmp/somewhere'; the_line='5'
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(sha256sum <<< "${the_line}:${the_string}")" \
            "$inFile"
echo -e '\n\n# --- Test case 3 -----'
the_string='cd $(SOME_UTIL_BIN); ./somecommand $(BUILD_DIRECTORY_PATH)/$(OBJ_DIR)/\$\^'; the_line='8'
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(sha256sum <<< "${the_line}:${the_string}")" \
           "$inFile"

更新：因为搜索的字符串非常复杂，这里有一个如何动态计算分隔符的示例（注意第 4 个测试用例）：

#!/usr/bin/env bash
sedReplace() {
    local the_searched_string="$1" the_replacement="$2" the_lenght="$3" the_file="$4" d="$5"

    if [[ $the_lenght == "$(grep -inF "$the_searched_string" "$the_file" | wc -c)" ]]
    then
        the_searched_string="$(sed -r 's/(\^|\$|\\)/./g' <<< "$the_searched_string")" # replace some special characters within the searched string by any char '.'
        the_expression="s${d}${the_searched_string}${d}${the_replacement}${d}"
        #echo "$the_expression"
        sed "$the_expression" "$the_file" #-i
    else
        echo "ERROR: Unhandled custom makefile modification (expected: ${the_searched_string})..."
        exit 1
    fi
}

get_delimiter() {
    unset delimiter

    for d in '/' ':' '#' '_' '|' '@'
    do
        if ! grep -qoF "$d" <<< "$the_string"
        then
            delimiter="$d"
            break
        fi
    done

    if [[ -z $delimiter ]]
    then
        echo 'There is not appropriate delimiter for the string:'
        echo "$the_string"
        exit 1
    fi
}

inFile="/tmp/makefileTest"

# Test all cases:
echo -e '\n\n# --- Test case 1 -----'
the_string='CFLAGS += -Wunused # this is a comment'
get_delimiter
sedReplace "$the_string" \
           'CFLAGS += -Wall # something is changed' \
           "$(wc -c <<< '2:'"$the_string")" \
           "$inFile" "$delimiter"

echo -e '\n\n# --- Test case 2 -----'
the_string='cp $(OBJ_DIR)/$(EXE_NAME) /tmp/somewhere'
get_delimiter
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(wc -c <<< '5:'"$the_string")" \
            "$inFile" "$delimiter"

echo -e '\n\n# --- Test case 3 -----'
the_string='cd $(SOME_UTIL_BIN); ./somecommand $(BUILD_DIRECTORY_PATH)/$(OBJ_DIR)/\$\^'
get_delimiter
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(wc -c <<< '8:'"$the_string")" \
           "$inFile" "$delimiter"

echo -e '\n\n# --- Test case 4 -----'
the_string='/:#_|@'
get_delimiter
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(wc -c <<< '8:'"$the_string")" \
           "$inFile" "$delimiter"

以下是上述内容的另一个版本：

#!/usr/bin/env bash
sedReplace() {
    local d the_searched_string="$1" the_replacement="$2" the_lenght="$3" the_file="$4"
    # the content of this function could be placed here, thus we will have only one function
    get_delimiter "$the_searched_string"

    if [[ $the_lenght == "$(grep -inF "$the_searched_string" "$the_file" | wc -c)" ]]
    then
        the_searched_string="$(sed -r 's/(\^|\$|\\)/./g' <<< "$the_searched_string")"
        the_expression="s${d}${the_searched_string}${d}${the_replacement}${d}"
        sed "$the_expression" "$the_file" #-i
    else
        echo "ERROR: Unhandled custom makefile modification (expected: ${the_searched_string})..."
        exit 1
    fi
}

get_delimiter() {
    # define an array of possible delimiters, it could be defined outside the function
    delimiters=('/' ':' '#' '_' '|' '@' '%')

    for delimiter in ${delimiters[@]}
    do
        if ! grep -qoF "$delimiter" <<< "$1"
        then
            d="$delimiter"
            break
        fi
    done

    if [[ -z $d ]]
    then
        echo "ERROR: There is not appropriate delimiter for the string: ${1}"
        exit 1
    fi
}

inFile="/tmp/makefileTest"

# Test all cases:
echo -e '\n\n# --- Test case 1 -----'
the_string='CFLAGS += -Wunused # this is a comment'
sedReplace "$the_string" \
           'CFLAGS += -Wall # something is changed' \
           "$(wc -c <<< '2:'"$the_string")" \
           "$inFile"

echo -e '\n\n# --- Test case 2 -----'
the_string='cp $(OBJ_DIR)/$(EXE_NAME) /tmp/somewhere'
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(wc -c <<< '5:'"$the_string")" \
            "$inFile"

echo -e '\n\n# --- Test case 3 -----'
the_string='cd $(SOME_UTIL_BIN); ./somecommand $(BUILD_DIRECTORY_PATH)/$(OBJ_DIR)/\$\^'
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(wc -c <<< '8:'"$the_string")" \
           "$inFile"

echo -e '\n\n# --- Test case 4 -----'
the_string='/:#_|@%'
sedReplace "$the_string" \
           "${the_string} # something is changed" \
           "$(wc -c <<< '8:'"$the_string")" \
           "$inFile"

Answer