2023年8月2日发(作者：)

shell脚本if语句的多种条件参数if语句有多种写法

[root sh]# [ -f file ] && echo "yes" || echo "no"

yes修改如下：if [ -f file ]

thenecho "yes"elseecho "no"fi简写：[ -f file ] && echo "yes"

表⽰if条件成⽴时返回yes[ -f file ] || echo "no"

表⽰if条件不成⽴时，返回no

可以⽤if判断如下条件：实际上if的条件就是test命令的参数[omcr@lnltedmr3 ~]$ man testTEST(1) User Commands TEST(1)NAME test - check file types and compare valuesSYNOPSIS test EXPRESSION test [ EXPRESSION ] [ ] [ OPTIONDESCRIPTION Exit with the status determined by EXPRESSION. --help display this help and exit --version output version information and exit An omitted EXPRESSION defaults to false. Otherwise, EXPRESSION is true or false and sets exit status. It is one of: ( EXPRESSION ) EXPRESSION is true ! EXPRESSION EXPRESSION is false EXPRESSION1 -a EXPRESSION2 both EXPRESSION1 and EXPRESSION2 are true EXPRESSION1 -o EXPRESSION2 either EXPRESSION1 or EXPRESSION2 is true -n STRING the length of STRING is nonzero STRING equivalent to -n STRING -z STRING the length of STRING is zero STRING1 = STRING2 the strings are equal STRING1 != STRING2 the strings are not equal INTEGER1 -eq INTEGER2 INTEGER1 is equal to INTEGER2 INTEGER1 -ge INTEGER2 INTEGER1 is greater than or equal to INTEGER2 INTEGER1 -gt INTEGER2 INTEGER1 is greater than INTEGER2 INTEGER1 -le INTEGER2 INTEGER1 is less than or equal to INTEGER2 INTEGER1 -lt INTEGER2 INTEGER1 is less than INTEGER2 INTEGER1 -ne INTEGER2 INTEGER1 is not equal to INTEGER2 FILE1 -ef FILE2 FILE1 and FILE2 have the same device and inode numbers FILE1 -nt FILE2 FILE1 is newer (modification date) than FILE2 FILE1 -ot FILE2 FILE1 is older than FILE2 -b FILE FILE exists and is block special -c FILE FILE exists and is character special -d FILE FILE exists and is a directory -e FILE FILE exists -f FILE FILE exists and is a regular file -g FILE FILE exists and is set-group-ID -G FILE FILE exists and is owned by the effective group ID -h FILE FILE exists and is a symbolic link (same as -L) -k FILE FILE exists and has its sticky bit set -L FILE FILE exists and is a symbolic link (same as -h) -O FILE FILE exists and is owned by the effective user ID -p FILE FILE exists and is a named pipe -r FILE FILE exists and read permission is granted -s FILE FILE exists and has a size greater than zero -S FILE FILE exists and is a socket -t FD file descriptor FD is opened on a terminal -u FILE FILE exists and its set-user-ID bit is set -w FILE FILE exists and write permission is granted -x FILE FILE exists and execute (or search) permission is granted Except for -h and -L, all FILE-related tests dereference symbolic links. Beware that parentheses need to be escaped (e.g., by backslashes) for shells. INTEGER may also be -l STRING, which evaluates to the length of STRING. NOTE: [ honors the --help and --version options, but test does not. test treats each of those as it treats any other nonempty STRING. NOTE: your shell may have its own version of test and/or [, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports. GNU coreutils online help: Report test translation bugs to AUTHOR Written by Kevin Braunsdorf and Matthew GHT Copyright © 2013 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later . This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by ALSO The full documentation for test is maintained as a Texinfo manual. If the info and test programs are properly installed at your site, the command info coreutils 'test invocation' should give you access to the complete coreutils 8.22 June 2018 TEST(1)