[英]how to tell if a script is executed from a pipe or not?
suppose we have this simple script(selfie.sh): 假设我们有这个简单的脚本(selfie.sh):
echo "$0"
how do i tell if it is executed this way sh selfie.sh
or not, such as cat selfie.sh | sh
我如何判断它是否以这种方式执行
sh selfie.sh
或者不是,例如cat selfie.sh | sh
cat selfie.sh | sh
? cat selfie.sh | sh
?
sh selfie.sh
give this: sh selfie.sh
给这个:
selfie.sh
and cat selfie.sh | sh
和
cat selfie.sh | sh
cat selfie.sh | sh
output this: cat selfie.sh | sh
输出这个:
sh
what I have tried: 我试过的:
[ -s "$0" ]
can't help if there's a file named 'sh' in pwd
pwd
有一个名为“sh”的文件,则[ -s "$0" ]
无法提供帮助 $BASH_SOURCE
or something alike is not compatible with POSIX shell $BASH_SOURCE
或类似的东西与POSIX shell不兼容 This question comes in front of me cause I have wrote a project named shell-utils , and I want the user could install like this way if this the first time (s)he installs: 这个问题摆在我面前因为我写了一个名为shell-utils的项目,我希望用户可以这样安装,如果这是他第一次安装:
curl -L https://raw.githubusercontent.com/oxnz/shell-utils/master/tool/install | sh
but if (s)he already has a copy of the software and invoke from his shell like this: 但如果(s)他已经拥有该软件的副本并从他的shell调用如下:
sh shell-utils/tool/install.sh
I need to tell the differences and act differently. 我需要说出差异并采取不同的行动。
Try the -t
conditional expression. 尝试使用
-t
条件表达式。
$ cat selfie.sh
[ -t 0 ] && echo "bash is reading a script from somewhere else" || echo "bash is reading a script from stdin"
$ cat selfie.sh | sh
bash is reading a script from stdin
$ sh selfie.sh
bash is reading a script from somewhere else
You can use the following POSIX-compliant shell function. 您可以使用以下符合POSIX标准的shell函数。
The only prerequisite is a Unix platform where stdin
is represented as file /dev/stdin
, which is generally the case nowadays. 唯一的先决条件是Unix平台,其中
stdin
表示为文件/dev/stdin
,现在通常就是这种情况。
You'll get a false positive only in one - very unusual - scenario: if, while sourcing a script, you also provide pipeline input; 你只会在一个非常不寻常的场景中得到误报:如果在获取脚本时,你还提供管道输入; eg,
echo hi | . selfie.sh
例如,
echo hi | . selfie.sh
echo hi | . selfie.sh
#!/bin/sh
# Indicates via exit code whether the contents of the script at hand
# were provided through a pipe, e.g., `curl .... | sh`.
# Caveat: You'll get a false positive in the following - exotic - corner case:
# ... | . script # combination of pipeline input and sourcing.
isThisScriptPiped() {
if [ ! -f "$0" ] || [ -x "$0" ] && POSIXLY_CORRECT=1 file -- "$0" | grep -Fvq 'text'; then
if POSIXLY_CORRECT=1 file -i /dev/stdin | grep -Fq 'fifo'; then
return 0
fi
fi
return 1
}
# Sample call
isThisScriptPiped && echo 'PIPED' || echo 'NOT piped'
Here's an annotated version of the same function: 这是相同功能的注释版本 :
#!/bin/sh
# Note: POSIXLY_CORRECT is set below to make the GNU `file` utility behave
# in a POSIX-compliant manner so as to report the type of the *target*
# in the event that the operand is a *symlink*.
# This *could* happen with a shell executable that is a symlink, and
# *definitely* happens with /dev/stdin, which on Linux is a symlink to
# /proc/self/fd/0.
# Indicates via exit code whether the contents of the script at hand
# were provided through a pipe, e.g., `curl .... | sh`.
# Caveat: You'll get a false positive in the following - exotic - corner case:
# ... | . script # combination of pipeline input and sourcing.
isThisScriptPiped() {
# Test 1 of 2: Check if $0 refers to:
# either: a nonexisting file (implies that $0 refers to an executable in
# the path)
# or: an executable file that is not text-based (not a shell script)
# Both cases imply that $0 refers to a shell executable, which in turn implies
# that no filename argument (script file path) was passed to the shell.
# Note that while `file` implementations differ, their output for text-based
# executables (shell scripts) always contains 'text' (POSIX mandates
# 'commands text', but neither BSD nor GNU `file` do that).
if [ ! -f "$0" ] || [ -x "$0" ] && POSIXLY_CORRECT=1 file -- "$0" | grep -Fvq 'text'; then
# The implication is that the script contents comes from:
# - either: stdin - whether through input redirection (sh < script) or
# from a pipe (... | sh)
# - or: from sourcing (. script)
# Note that in sh there is no way that I know of that lets you determine
# reliably whether the script is being sourced. Knowing whether the script
# is being sourced *or* provided via stdin is as close as you can get.
# (To check for sourcing in Bash, Ksh, or Zsh, see
# http://stackoverflow.com/a/28776166/45375 )
# Test 2 of 2:
# See if stdin is connected to a pipe, which in combination with test 1
# implies that the script contents is being piped, EXCEPT in one scenario:
# Caveat: You'll get a false positive in the following - very unusual -
# corner case:
# ... | . script # combination of sourcing and pipe input
# Note:
# - POSIX mandates that when passing a FIFO (named pipe) to `file`
# the output contain the string 'fifo', which is true of both BSD
# and GNU `file`.
# - Option -i is crucial to prevent `file` from trying to
# read the *contents* of stdin; with -i, it just reports the basic
# file type.
if POSIXLY_CORRECT=1 file -i /dev/stdin | grep -Fq 'fifo'; then
return 0
fi
fi
return 1
}
# Sample call
isThisScriptPiped && echo 'PIPED' || echo 'NOT piped'
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