如何將另一個(gè)值附加到go環(huán)境變量的現(xiàn)有值？如果CGO_CXXFLAGS 的值為“-I/blah/blah”由于以下不起作用$ go env -w CGO_CXXFLAGS="$CGO_CXXFLAGS -I/foo/bar"我想找到一個(gè)正確的方法讓CGO_CXXFLAGS具有值“-I/blah/blah -I/foo/bar”通過避免簡(jiǎn)單地重新設(shè)置所有值加上新值，例如：$ go env -w CGO_CXXFLAGS="-I/blah/blah -I/foo/bar"
1 回答
Qyouu
TA貢獻(xiàn)1786條經(jīng)驗(yàn) 獲得超11個(gè)贊
由于go env <var_name> 輸出變量的有效設(shè)置（即不一定是默認(rèn)值），獲取環(huán)境變量當(dāng)前默認(rèn)值的可靠方法是使用子 shell（假設(shè)是 Bash shell）：
$ (unset <var_name>; go env <var_name>)
然后，要設(shè)置一個(gè)新值，您需要使用命令替換：
$ go env -w <var_name>="$(unset <var_name>; go env <var_name>)<value_to_append>"
有關(guān)工作示例，請(qǐng)參閱以下帶注釋的日志：
# Write an initial default.
$ go env -w CGO_CXXFLAGS=-I/blah/blah
$ go env CGO_CXXFLAGS
-I/blah/blah
# Keep in mind that the default can be overridden by a currently set
# environment variable.
$ export CGO_CXXFLAGS="-I/override/default"
$ go env CGO_CXXFLAGS
-I/override/default
# To print the default value even when it is being overridden,
# in a subshell, unset the environment variable and then run 'go env'.
$ (unset CGO_CXXFLAGS; go env CGO_CXXFLAGS)
-I/blah/blah
# To set a new default value utilizing the existing default value.
#
# Note: if the default isn't being overridden, no warning will be printed.
$ go env -w CGO_CXXFLAGS="$(unset CGO_CXXFLAGS; go env CGO_CXXFLAGS) -I/foo/bar"
warning: go env -w CGO_CXXFLAGS=... does not override conflicting OS environment variable
# State after change...
# Default value
$ (unset CGO_CXXFLAGS; go env CGO_CXXFLAGS)
-I/blah/blah -I/foo/bar
# Overridden value
$ go env CGO_CXXFLAGS
-I/override/default
或者，您可以找到具有默認(rèn)值的文件并直接解析它（go env GOENV會(huì)告訴您文件位置），但我認(rèn)為暫時(shí)取消設(shè)置環(huán)境變量并讓其完成go env工作會(huì)更容易。
PowerShell 中的等價(jià)物：
# Write default.
PS > go env -w CGO_CXXFLAGS=-I/blah/blah
PS > go env CGO_CXXFLAGS
-I/blah/blah
# Override default.
PS > $Env:CGO_CXXFLAGS = "-I/override/default"
PS > go env CGO_CXXFLAGS
-I/override/default
# Print default.
PS > Start-Job {$Env:CGO_CXXFLAGS=''; go env CGO_CXXFLAGS} | Receive-Job -Wait
-I/blah/blah
# Append to default.
PS > go env -w CGO_CXXFLAGS="$(Start-Job {$Env:CGO_CXXFLAGS=''; go env CGO_CXXFLAGS} | Receive-Job -Wait) -I/foo/bar"
warning: go env -w CGO_CXXFLAGS=... does not override conflicting OS environment variable
# Final state.
PS > go env CGO_CXXFLAGS
-I/override/default
PS > Start-Job {$Env:CGO_CXXFLAGS=''; go env CGO_CXXFLAGS} | Receive-Job -Wait
-I/blah/blah -I/foo/bar
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